JP2010026921A - Positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positioning device which is relatively inexpensive as a whole while ensuring high positioning accuracy in a specific area. <P>SOLUTION: The positioning device includes: a slider 1 to be position-controlled; a platen 10 having teeth of magnetic poles formed in a face opposite to the slider 1 thereof to constitute a planar motor with the slider 1; resolvers 30a-30c (resolver 30) which detect the position of the slider 1; laser interferometers 20a and 20b (laser interferometer 20) which detect the position of the slider 1 in a specific area A of the platen 10 with accuracy higher than that of the resolver 30; a switch 100c which selects either one position detector of the resolver 30 and the laser interferometer 20 according to the position of the slider 1; and a position control part 102 which executes position control of the slider 1 based on a position instruction value and a position detection value detected by the position detector selected by the switch 100c. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a positioning device, and more particularly to a positioning device that controls the position of a slider with respect to a platen constituting a planar motor.

  FIG. 13 is a block diagram showing an example of a conventional positioning device. A quadrilateral slider is mounted on the quadrilateral platen 10, and position control is performed on the platen 10 in the X-axis direction and the Y-axis direction. Magnetic pole teeth (hereinafter simply referred to as teeth) having a predetermined pitch are formed on the opposing surfaces of the platen 10 and the slider to constitute a planar motor. By driving the flat motor, the slider moves to a designated position.

  Bar mirrors are provided on three sides of the slider. A plurality of laser interferometers that detect the position of the slider are fixedly disposed on the sides 10 a to 10 c of the platen 10. The laser interferometers arranged on one opposing side 10a, 10b of the platen detect the position of the slider in the X-axis direction, and the laser interferometers arranged on the side 10c detect the position of the slider in the Y-axis direction. The laser interferometer detects the position of the slider with high accuracy based on the interference between the emitted laser light and the reflected light that is reflected by the bar mirror of the slider and returned. More specifically, the laser interferometer outputs a detection signal corresponding to the distance between the laser interferometer and the bar mirror based on the interference with the reflected light, and the position of the slider is calculated based on the detection signal.

  The position range of the slider whose position can be detected by the laser interferometer is limited to a position immediately before the reflected light from the bar mirror of the slider comes off the laser interferometer. Therefore, a plurality of laser interferometers are provided along the moving direction of the slider, and the slider is moved in all areas where the slider can move by switching the laser interferometer to be used from among the plurality of laser interferometers as the slider moves. Position detection is possible.

  The laser interferometers arranged on the sides 10a and 10b of the platen 10 each detect the position of the slider in the X-axis direction at two points to determine the rotation angle θ of the slider. The detected position and rotation angle θ of the slider are fed back to the planar motor and used for slider position control and attitude control. Patent Document 1 listed below describes a positioning device that detects the position of a slider using a laser interferometer.

JP2007-163418A

  However, depending on the use of the positioning device, high positioning accuracy is not necessarily required in all areas in which the slider can move, and it may be necessary to obtain high positioning accuracy only in a specific area. In such a case, the position detection accuracy of the laser interferometer becomes overspec in areas other than the specific area.

  Since the laser interferometer is an expensive part, detecting the position using the laser interferometer up to an over-special area leads to unnecessary cost increase of the positioning device.

  Further, in the position detection system that involves switching of the laser interferometer as described above, errors that occur at the time of laser interferometer switching are accumulated in the position detection value. Therefore, the original position detection accuracy of the laser interferometer may not be obtained even in a specific area where high positioning accuracy is required.

  An object of the present invention is to provide a positioning device that is relatively inexpensive as a whole while eliminating the problems of conventional devices and ensuring high positioning accuracy in a specific area.

In order to achieve the above object, the invention of claim 1
In a positioning apparatus comprising a slider whose position is controlled, and a platen in which magnetic pole teeth are formed on a surface facing the slider and the slider and a flat motor are configured.
A first position detecting device for detecting the position of the slider;
A second position detection device that detects the position of the slider in a specific area of the platen with higher accuracy than the first position detection device;
Switching means for selecting either the first or second position detecting device according to the position of the slider;
A position control unit that performs position control of the slider based on a position command value and a position detection value detected by a position detection device selected by the switching means;
It is provided with.

The invention of claim 2
The positioning device according to claim 1, further comprising a correction unit that performs correction to maintain the slider at the same position before and after switching between the first and second position detection devices.

The invention of claim 3
The positioning device according to claim 2, wherein the correction unit, when the switching unit switches the position detection device, based on a detection error of the first position detection device, The position detection value detected by the position detection device is corrected.

The invention of claim 4
4. The positioning device according to claim 3, wherein the detection error of the first position detection device is a detection error specific to a tooth corresponding to the current position of the slider of the platen.

The invention of claim 5
4. The positioning device according to claim 3, wherein the detection error of the first position detection device is a detection error that appears in synchronization with a tooth pitch of the platen.

The invention of claim 6
The positioning device according to any one of claims 1 to 5, wherein the first position detection device is a resolver provided on the slider,
The second position detecting device is a laser interferometer.

According to the invention of claim 1,
A first position detection device; and a second position detection device that detects the position of the slider in a specific area of the platen with higher accuracy than the first position detection device. By properly using the position detection device, it is possible to provide a relatively inexpensive positioning device as a whole while ensuring high positioning accuracy in a specific area.

According to the invention of claim 2,
Since a correction unit that performs correction to maintain the slider at the same position before and after switching between the first and second position detection devices is provided, it is possible to prevent abrupt movement of the slider that occurs when the position detection device is switched.

According to the invention of claim 3,
The correction unit corrects the position command value and the position detection value detected by the second position detection device based on a detection error of the first position detection device when switching the position detection device. The abrupt movement of the slider caused by the detection error of the first position detecting device can be prevented.

According to the invention of claim 4,
Since the detection error of the first position detection device is a detection error inherent to the tooth corresponding to the current position of the slider of the platen, the position detection device can be used even when the platen teeth are uneven or have a processing error. Regardless of the switching position, sudden movement of the slider can be reliably prevented.

According to the invention of claim 5,
Since the detection error of the first position detection device is a detection error that appears in synchronization with the tooth pitch of the platen, the slider position at the time of switching the position detection device and the platen tooth corresponding to the slider position Regardless of the relative positional relationship, abrupt movement of the slider can be reliably prevented.

According to the invention of claim 6,
Since the first position detection device is a resolver and the second position detection device is a laser interferometer, the laser interferometer ensures high position detection accuracy, and the resolver reduces the cost of the entire positioning device. Can do.

  In the first embodiment, a resolver is used as the first position detection device that detects the position of the slider, and a laser interferometer is used as the second position detection device. The main components constituting the resolver are a core and a coil, and the structure is simple and inexpensive compared to other sensors such as a laser interferometer. In addition, since the resolver core and the coil are both highly durable, maintenance is easy. First, the operation principle of the resolver will be described.

  FIG. 1 is an explanatory diagram of an operation principle in which a resolver outputs a signal corresponding to a position. The resolver sensor unit 200 includes a core 201 and a coil 202 wound around the core 201. The sensor unit 200 is disposed on the platen 10 via a predetermined gap. Teeth are formed on the surface of the core 201 facing the platen 10 at the same pitch L as the teeth of the platen 10.

  Between the platen 10 and the core 201, an impedance Z corresponding to the relative position of the teeth of the platen 10 and the teeth of the core 201 exists. When a rectangular voltage having a constant amplitude is input to the coil 201 as an excitation voltage, the core 201 is excited and a magnetic circuit B is formed between the coil 201 and the platen 10. Since the magnetic circuit B is affected by the impedance Z, as a result, the voltage between the terminals of the coil 202 changes according to the relative position of the platen 10 and the core 201. Therefore, the voltage between the terminals of the coil 202 is taken out and its amplitude is used as a detection signal.

FIG. 1A shows a relative position where the facing area between the teeth of the core 201 and the teeth of the platen 10 is maximum, that is, the phase difference is 0 °. At this time, the impedance Z is minimized and the detection signal is maximized.
On the other hand, FIG. 1B shows a relative position where the facing area between the teeth of the core 201 and the teeth of the platen 10 is minimum, that is, the phase difference is 180 °. At this time, the impedance Z is maximized and the detection signal is minimized.

  When the sensor unit 200 moves on the platen 10, the impedance Z changes in a sine wave shape. Therefore, the detection signal changes in a sine wave shape with a pitch L as shown in FIG.

  The resolver is configured by preparing two sets of such sensor units 200 and shifting the phase with respect to the platen 10 by 90 ° as shown in FIG. The phase difference of the resolver with respect to the platen 10, that is, the relative position of the platen 10 with respect to the teeth is obtained by taking one of the sensor units 200 as the sin phase and the other as the cos phase and taking the arc tangent of the detection signals obtained from these sensor units. It is done. The relative position of the platen 10 with respect to which tooth is obtained by counting the number of sine wave peaks that the detection signal repeats from the origin position. As described above, a signal corresponding to the position from the origin position can be extracted by the resolver. In general, a laser interferometer has higher position detection accuracy than a resolver.

FIG. 3 is a top view showing the configuration of the positioning device of the present embodiment.
The slider 1 is mounted on the platen 10 using an air bearing. Teeth 10a, 1a having a constant pitch L are formed on the opposing surfaces of the platen 10 and the slider 1 in the X-axis direction and the Y-axis direction to constitute a planar motor. The position of the slider 1 is controlled on the platen 10 in the X-axis direction, the Y-axis direction, and the θ-axis direction by the planar motor. In this figure, some of the teeth of the platen 10 are omitted.

  The slider 1 has a rectangular shape, and each side of the slider 1 is disposed on the platen 10 along either the X axis or the Y axis perpendicular to the X axis.

  A laser interferometer 20a is fixedly arranged on the side along the Y axis of the platen 10, and a laser interferometer 20b is fixedly arranged on the side along the X axis. A bar mirror 21a is mounted on the side of the slider 1 facing the laser interferometer 20a, and a bar mirror 21b is mounted on the side facing the laser interferometer 20b. The laser interferometer 20a detects the X position of the slider 1, and the laser interferometer 20b detects the Y position of the slider 1. Further, the laser interferometer 20b inspects two Y positions of the slider 1 and detects the rotation angle θ of the slider 1 based on the difference between the detected Y positions.

  Furthermore, resolvers 30 a to 30 c are provided on the slider 1. The resolvers 30 a to 30 c are embedded in the edge portion of the surface of the slider 1 facing the platen 10. The resolvers 30a and 30b are embedded in the center portion of the slider 1 in the X-axis direction, and the resolver 30c is embedded in the center portion of the slider 1 in the Y-axis direction. The resolvers 30 a and 30 b have teeth formed at a constant pitch L in the X-axis direction on the surface facing the platen 10, and detect the X position of the center portion of the slider 1. The resolver 30 c has teeth formed at a constant pitch L in the Y-axis direction on the surface facing the platen 10, and detects the Y position of the center portion of the slider 1. Further, the rotation angle θ of the slider 1 is detected based on the difference between the X positions detected by the resolvers 30a and 30b.

  The detection signals Oia and Oib of the laser interferometers 20a and 20b and the detection signals Ora, Orb and Orc of the resolvers 30a to 30c are digitized by A / D converters (not shown) and then input to the arithmetic unit 100 (not shown). The The calculation unit 100 calculates the current position and rotation angle of the slider 1 based on these detection signals. The calculated current position and rotation angle of the slider 1 are fed back to the planar motor and used for position control and attitude control of the slider 1.

  Hereinafter, the laser interferometers 20a and 20b are described as the laser interferometer 20, and the resolvers 30a to 30c are described as the resolver 30. Further, when the detection signals Oia and Oib are represented, they are described as a detection signal Oi, and when the detection signals Ora, Orb and Orc are represented, they are described as a detection signal Or.

FIG. 4 is a diagram illustrating area division of the platen 10. Area A is an area where high positioning accuracy is required for the slider 1 on the platen 10. Area B is an area other than area A on platen 10 and is an area that does not require as high positioning accuracy as area A.
Hereinafter, “slider 1 is located in area A” means that the entire slider 1 is in area A, and “slider 1 is located in area B” means that at least a part of slider 1 is It means the state that is out of area A.

  When the slider 1 is located in the area A, the position of the slider 1 is detected by the laser interferometer 20. When the slider 1 is located in the area B, the resolver 30 detects the position of the slider 1.

The resolver 30 can detect the position on the entire surface of the platen 10, but the laser interferometer 20 has a limited range in which the position can be detected depending on the position of the slider 1. The range of the slider 1 in which the position can be detected by the laser interferometer 20 is the position immediately before the reflected light from the bar mirror 21a is removed from the laser interferometer 20a. The range of the slider 1 in the X-axis direction is up to a position immediately before the reflected light from the bar mirror 21b is detached from the laser interferometer 20b. Therefore, the attachment positions of the laser interferometers 20a and 20b, the sizes of the bar mirrors 21a and 21b, and the size of the slider 1 are determined according to the position and size of the area A.
When the slider 1 is located in the area B, the position detection value by the laser interferometer 20 is indefinite.

FIG. 5 is a block diagram showing details of the positioning device of the present embodiment.
The positioning device includes a position control unit 102, a slider 1, a laser interferometer 20, a resolver 30, and a calculation unit 100. The computing unit 100 includes measurement processing units 100a and 100b, a changeover switch 100c, a coordinate establishment unit 100d, and a correction unit 100e. The positioning device is given various instruction signals and position command values for the slider 1 from the host device.

  The position command value generation unit 101 is included in the host device and generates a position command value Pcmd for the slider 1. The position control unit 102 is given a position command value Pcmd from the position command value generation unit 101. The position command value Pcmd is a signal indicating coordinates (Xcmd, Ycmd, θcmd) to which the slider 1 is to be moved, that is, a target position. The position control unit 102 converts the position command value Pcmd into a drive current supplied to the planar motor of the slider 1 and moves the slider 1.

  The detection signal Oi from the laser interferometer 20 is input to the measurement processing unit 100a. Further, the detection signal Or of the resolver 30 is input to the measurement processing unit 100b. The measurement processing unit 100a converts the input detection signal Oi into a position detection value Pi (Xi, Yi, θi) and outputs it to the switching means 100c. Further, the measurement processing unit 100b converts the input detection signal Or into a position detection value Pr (Xr, Yr, θr), and outputs it to the changeover switch 100c.

  The changeover switch 100c changes over to one of the position detection values Pi and Pr in accordance with a change instruction signal S1 given from the host device. The changeover switch 100c feeds back the selected position detection value to the position control unit 102 as a position feedback signal Pfb. The position control unit 102 servo-controls the slider 1 so that the deviation between the feedback signal Pfb and the position command value Pcmd becomes zero.

  The switching instruction signal S1 is switched to select the position detection value Pi when the slider 1 moves from the area B to the area A, and selects the position detection value Pr when the slider 1 moves from the area A to the area B. Are switched as follows. Thereby, the laser interferometer 20 and the resolver 30 are switched.

Next, the operation at the time of switching between the laser interferometer 20 and the resolver 30 will be described.
A case where the slider 1 moves from the area B to the area A and a case where the slider 1 moves from the area A to the area B will be described in order.

<When moving from area B to area A>
An operation of establishing position detection by the laser interferometer 20 from position detection by the resolver 30 is performed.

  Laser interferometer 20 has an indefinite position detection value in area B, and laser interferometer 20 is an increment type detection device. Therefore, in order to establish position detection by the laser interferometer 20, it is necessary to give an initial value at the time when the position detection by the laser interferometer 20 is started after the slider 1 enters the area A (step ST1).

  The coordinate establishing unit 100d receives the position detection value Pr from the measurement processing unit 100b. Further, after the slider 1 enters the area A, the coordinate establishing unit 100d receives an establishment instruction signal S2 instructing establishment of position detection by the laser interferometer 20 from the host device. The coordinate establishing unit 100d outputs the position detection value Pr to the measurement processing unit 100a in response to the input of the establishment instruction signal S2. The measurement processing unit 100a presets the input position detection value Pr as the position detection value Pi (step ST2). Thereafter, the switching unit 100c switches the position detection value from Pr to Pi (step ST3).

  By the way, when the position of the slider 1 is detected by the resolver 30, a position detection error E (Ex, Ey, Eθ) corresponding to the position of the slider 1 appears in the position detection value Pr. By presetting the position detection value Pr to the position detection value Pi, the position detection error E is continuously added to the subsequent position detection value Pi. Since high position detection accuracy is required in area A, it is necessary to correct this position detection error E from the position detection value Pi.

  The correction unit 100e corrects the position detection error E. The position detection value Pr is input from the measurement processing unit 100b to the correction unit 100e. Further, the correction unit 100e receives a correction instruction signal S3 for instructing correction of the position detection error E from the host device. In the correction unit 100e, the position detection value Pr and the position detection error E at that position are associated in advance. The correction unit 100e obtains a position detection error E corresponding to the position detection value Pr according to the input of the correction instruction signal S3, and outputs the position detection error E to the measurement processing unit 100a. The measurement processing unit 100a subtracts the position detection error E from the preset position detection value Pr to obtain an initial value of the position detection value Pi (step ST4). Thereby, the position detection error E is removed from the position detection value Pi. That is, the position detection error E is removed from the position feedback signal Pfb after switching.

  By correcting the position detection value Pi with the position detection error E, the position feedback signal Pfb and the position command value Pcmd become different values. In order to keep the position feedback signal Pfb and the position command value Pcmd at the same value, the position detection error E is also corrected for the position command value Pcmd.

  The correction unit 100e outputs the position detection error E to the position command value generation unit 101 together with the measurement processing unit 100a. The position command value generation unit 101 subtracts the position detection error E from the position command value Pcmd, and outputs this as a new position command value Pcmd (step ST5). Thereby, the position command value Pcmd and the position feedback signal Pfb are kept in agreement before and after switching by the changeover switch 100c.

  Step ST4 and step ST5 are performed simultaneously. When a period in which the position command value Pcmd and the position feedback signal Pfb deviate occurs, the deviation between the position command value Pcmd and the position feedback signal Pfb changes instantaneously. This is because the position control unit 102 suddenly moves the slider 1 due to an instantaneous change in the deviation, and the workpiece mounted on the slider 1 may be damaged due to excessive acceleration. .

Steps ST2 to ST5 are performed in a state where the slider 1 is positioned at the same point on the platen 10. Further, step ST4 and step ST5 are performed immediately after step ST3 or simultaneously with step ST3.
As described above, position detection by the laser interferometer 20 is established.

<When moving from area A to area B>
An operation of shifting from position detection by the laser interferometer 20 to position detection by the resolver 30 is performed.

  The operation of shifting to position detection by the resolver 30 is performed in a state where the slider 1 is positioned in the area A. When the slider 1 is located in the area A, both position detection values Pi and Pr are obtained. The position detection value Pr includes a position detection error E. Since this position detection error E depends on the position of the slider 1, it differs from the position detection error value used for correction when the laser interferometer 20 is established. Therefore, usually, the position detection value Pi and the position detection value Pr do not match (step ST6).

  In this state, when the changeover switch 100c is switched from the position detection value Pi to Pr, the position feedback signal diverges before and after the changeover. Therefore, the position detection error E is corrected again by the correction unit 100e.

  The correction instruction signal S3 is input again to the correction unit 100e from the host device, and a position detection error E corresponding to the position detection value Pr is obtained. The correction unit 100e outputs the obtained position detection error E to the measurement processing unit 100a. The measurement processing unit 100a adds the position detection error E to the current position detection value Pi and outputs it as a new position detection value Pi (step ST7). As a result, the position detection value Pi matches the position detection value Pr.

  Further, the correction unit 100e outputs a position detection error E to the position command value generation unit 101. The position command value generation unit 101 adds the position detection error E to the position command value Pcmd, and outputs this as a new position command value Pcmd (step ST8). Step ST8 is performed simultaneously with step ST7. Thereafter, the switching unit 100c switches the position detection value from Pi to Pr (step ST9). As a result, the position command value Pcmd and the position feedback signal Pfb are kept in agreement before and after switching by the changeover switch 100c.

Steps ST7 to ST9 are performed in a state where the slider 1 is positioned at the same point on the platen 10. Further, steps ST7 and ST8 are performed immediately before step ST9 or simultaneously with ST9.
Thus, the transition to position detection by the resolver 30 is completed.
Thereafter, when the slider 1 leaves the area A, the laser interferometer 20 cannot obtain the detection signal Oi, and the position detection value Pi becomes indefinite.

  In FIG. 5, the position command value generation unit 101, the position control unit 102, and the calculation unit 100 are shown only by functional blocks.

  6A and 6B are diagrams showing changes in the values of the respective signals when the position detection device is switched. FIG. 6A shows a case where the slider 1 moves from the area B to the area A. FIG. This is a change in signal when moving to B. For simplicity, only the value in the X-axis direction is shown.

  In step ST1, the position command value Xcmd and the position detection value Xr are both 10000. Since the laser interferometer 20 is not established, the position detection value Xi is indefinite. The position detection error Ex = + 50 when the position detection value Xr = 10000, and the slider 1 is actually positioned at X = 9950.

  The position detection value Xr is preset to the position detection value Xi, and Xi = 10000 (step ST2). Thereafter, the position detection device is switched from the resolver 30 to the laser interferometer 20 by the changeover switch 100c (step ST3). Further, the position detection error Ex is subtracted from the position detection value Xi to obtain Xi = 9950 (step ST4), and the position detection error Ex is subtracted from the position command value Xcmd to obtain Xcmd = 9950 (step ST5). Since step ST4 and step ST5 are performed simultaneously, the position command value Xcmd and the position feedback signal Xfb always match before and after switching. Therefore, the slider 1 does not move before and after switching.

  In step ST6, the position command value Xcmd, the position detection value Xi, and the slider position are all 20000. When the slider 1 is at this position, in the position detection by the resolver 30, the position detection value Xr = 19900 and the position detection error Ex = −100.

  The position detection error Ex is added to the position detection value Xi to be Xi = 19900 (step ST7), and the position detection error Ex is added to the position command value Xcmd to be Xcmd = 19900 (step ST8). Thereafter, the position detection device is switched from the laser interferometer 20 to the resolver 30 by the changeover switch 100c (step ST9). Since step ST7 and step ST8 are performed simultaneously, the position command value Xcmd and the position feedback signal Xfb always match before and after switching. Therefore, the slider 1 does not move before and after switching.

Next, the position detection error E (Ex, Ey, Eθ) will be described.
In this embodiment, the position detection error E is divided into two types, an error that appears in synchronization with the tooth pitch of the platen (position detection error Ea) and an error that is unique to each tooth of the platen 10 (position detection error Eb). To obtain the error value. The position detection errors Ea and Eb are measured for each of the X-axis direction, the Y-axis direction, and the θ-axis direction. The position detection error E is acquired prior to actual operation, such as when the positioning device is manufactured.

First, the position detection error Ea (Eax, Eay, Eaθ) will be described.
The resolver 30 generates a detection signal based on the relative position of the platen 10 with respect to the teeth 10a. Therefore, a position detection error appears in the detection signal of the resolver 30 in the period of the tooth pitch L.

  FIG. 7 is an enlarged view of the teeth 10 a of the platen 10. The tooth 10a is divided into a plurality of areas in a lattice shape, and a position detection error Ea that occurs when the slider 1 is positioned at each lattice point is measured. For the position detection error, a positioning mark is attached to the upper surface of the slider 1, the actual position of the positioning mark is observed with a camera fixed above the platen 10, and the observed position is compared with a theoretical value. Ask by. Note that the suffix p is added to indicate the position in the X-axis direction and the Y-axis direction in the tooth 10a.

  In FIG. 7, the lattice point at the position (Xp [m], Yp [n]) is B1, the lattice point at the position (Xp [m], Yp [n + 1]) is B2, and the position (Xp [m + 1]) , Yp [n + 1]) is B3, and the lattice point at position (Xp [m + 1], Yp [n]) is B4.

  FIG. 8 is a diagram showing the position detection error Ea, and is an enlarged view of the shaded portion of FIG. 8A shows the position detection error Eax in the X-axis direction, FIG. 8B shows the position detection error Eay in the Y-axis direction, and FIG. 8C shows the position detection error Eaθ in the θ-axis direction.

  The position detection error Ea inside each area divided by each grid point is obtained by interpolating from the position detection errors at surrounding grid points. For example, the position detection errors Eax, Eay, Eaθ at the point B (xp, yp) in the figure are calculated by interpolation from the position detection errors at the grid points B1 to B4 that delimit the area where the point B exists.

The position detection errors in the X-axis direction at the lattice points B1 to B4 are respectively expressed as Eax [m] [n], Eax [m] [n + 1], Eax [m + 1] [n + 1], and Eax [m + 1] [n]
, The position detection error Eax at the point B can be expressed as follows.

The position detection errors in the Y-axis direction at the lattice points B1 to B4 are respectively expressed as Eay [m] [n], Eay [m] [n + 1], Eay [m + 1] [n + 1], and Eay [ m + 1] [n]
, The position detection error Eay at point B can be expressed as follows.

The position detection errors in the θ-axis direction at the lattice points B1 to B4 are respectively expressed as Eaθ [m] [n], Eaθ [m] [n + 1], Eaθ [m + 1] [n + 1], Eaθ [ m + 1] [n]
, The position detection error Eaθ at the point B can be expressed as follows.

Next, the position detection error Eb (Ebx, Eby, Ebθ) will be described.
The teeth 10a of the platen 10 have uneven teeth due to processing errors. Therefore, a unique error appears for each tooth in the detection signal of the resolver 30.

  FIG. 9 is a view showing the platen 10. The platen 10 is divided into a plurality of areas in a lattice shape, and a position detection error Eb that occurs when the slider 1 is positioned at each lattice point is obtained. The position detection error of FIG. 9 is obtained by attaching a positioning mark on the upper surface of the slider 1, observing the actual position of the positioning mark with a camera fixed above the platen 10, and calculating the observed position as a theoretical value. By comparing with

  Note that when the observed value of the position detection error is Eb ′, the observed value Eb ′ includes the position detection error Ea. Therefore, the position detection error Eb is obtained by subtracting the position detection error Ea from the observed value Eb ′.

  In FIG. 9, the lattice point at position (X [h], Y [k]) is C1, the lattice point at position (X [h], Y [k + 1]) is C2, and the position (X [h + 1] , Y [k + 1]) as C3, and the lattice point at position (X [h + 1], Y [k]) as C4.

  FIG. 10 is a diagram showing the position detection error Eb, and is an enlarged view of the shaded portion of FIG. 10A shows a position detection error Ebx in the X-axis direction, FIG. 10B shows a position detection error Eby ′ in the Y-axis direction, and FIG. 10C shows a position detection error Ebθ ′ in the θ-axis direction.

  The position detection error Eb inside each area divided by each grid point is obtained by interpolating from the position detection errors at surrounding grid points. For example, the position detection errors Ebx, Eby, Ebθ at the point C (x, y) in the figure are calculated by interpolating from the position detection errors at the grid points C1 to C4 that delimit the area where the point C exists.

The position detection errors in the X-axis direction at the lattice points C1 to C4 are respectively expressed as Ebx [h] [k], Ebx [h] [k + 1], Ebx [h + 1] [k + 1], Ebx [h + 1] [k]
, The position detection error Ebx at the point C can be expressed as follows.

Further, the position detection errors in the Y-axis direction at the lattice points C1 to C4 are respectively expressed as Eby [h] [k], Eby [h] [k + 1], Eby [h + 1] [k + 1], and Eby [ h + 1] [k]
, The position detection error Eby at the point C can be expressed as follows.

Further, the position detection errors in the θ-axis direction at the lattice points C1 to C4 are respectively expressed as Ebθ [h] [k], Ebθ [h] [k + 1], Ebθ [h + 1] [k + 1], Ebθ [ h + 1] [k]
, The position detection error Ebθ at the point C can be expressed as follows.

  The correction unit 100e stores position detection errors Ea corresponding to lattice points B1, B2,... That divide the teeth 10a of the platen 10 into a plurality of areas, and lattice points that divide the entire platen 10 into a plurality of areas. The position detection error Eb corresponding to C1, C2,. Then, the correction unit 100e adds these position detection errors Ea and Eb to obtain a position detection error E.

That is, the correction unit 100e is configured according to the position of the slider 1.
Position detection error Ex = Eax + Ebx (7)
Position detection error Ey = Eay + Eby (8)
Position detection error Eθ = Eaθ + Ebθ (9)
And the position detection error E is calculated.

This embodiment is configured as described above,
A resolver 30 that detects the position of the slider 1, and a laser interferometer 20 that detects the position of the slider 1 in the area A of the platen 10 with higher accuracy than the resolver 30, and the resolver 30 according to the position of the slider 1, By properly using the laser interferometer 20, it is possible to provide a relatively inexpensive positioning device as a whole while ensuring high positioning accuracy in the area A.

  In addition, since the correction unit 100e that performs correction to maintain the slider 1 at the same position before and after switching between the resolver 30 and the laser interferometer 20, the jump of the slider position that occurs at the time of switching can be prevented.

  The correction unit 100e corrects the position command value Pcmd and the position detection value Pi detected by the laser interferometer 20 based on the position detection error E of the resolver 30 when switching between the resolver 30 and the laser interferometer 20. Therefore, the jump of the slider position caused by the position detection error E of the resolver 30 can be prevented.

  Further, since the position detection error E of the resolver 30 includes a detection error Eb inherent to the tooth corresponding to the current position of the slider 1 of the platen 10, even if the teeth of the platen 10 have irregularities or processing errors, Regardless of the switching position of the resolver 30 and the laser interferometer 20, it is possible to reliably prevent the slider position from jumping.

  Further, since the position detection error E of the resolver 30 includes a position detection error Ea that appears in synchronization with the tooth pitch L of the platen 10, the slider position at the time of switching between the resolver 30 and the laser interferometer 20, and the slider position. The slider position can be reliably prevented from jumping regardless of the relative positional relationship with the teeth of the platen 10 corresponding to.

  In the present embodiment, the position detection error Eb can be calculated over the entire surface of the platen 10. However, when the position where the resolver 30 and the laser interferometer 20 are switched is limited to a specific position on the platen 10, the position detection error Eb stored in the correction unit 100e may be the amount corresponding to the switching position. Good.

  In this embodiment, the resolver 30 corresponds to the first position detection device in the claims, the laser interferometer 20 corresponds to the second position detection device, and the changeover switch 100c corresponds to the switching means.

  FIG. 11 is a top view showing Embodiment 2 of the present invention. This embodiment has two areas where high positioning accuracy is required compared to the first embodiment.

  The platen 11 is divided into three areas: area A1, area A2, and area B. Areas A1 and A2 are areas where high positioning accuracy is required, and correspond to area A of the first embodiment. Area B1 corresponds to area B of the first embodiment. A slider 1 is mounted on the platen 11.

  Laser interferometers 20a and 20c are fixedly arranged on the side of the platen 11 along the Y axis, and a laser interferometer 20b is fixedly arranged on the side along the X axis. Laser interferometer 20a corresponds to area A1, and laser interferometer 20c corresponds to area A2.

  When the slider 1 is located in the area A1, the position of the slider 1 is detected using the laser interferometers 20a and 20b. When the slider 1 is located in the area A2, the position of the slider 1 is detected using the laser interferometers 20c and 20b. When the slider 1 is located in the area B1, the resolver 30 detects the position of the slider 1. Other configurations are the same as those of the first embodiment.

  The present embodiment is configured as described above. In addition to the effects obtained in the first embodiment, even when there are a plurality of areas on the platen 11 where high positioning accuracy is required, the minimum number of laser interferometers is used. In these areas, it is possible to provide a relatively inexpensive positioning device as a whole while ensuring high positioning accuracy.

  FIG. 12 is a top view showing Embodiment 3 of the present invention. In this embodiment, two positioning devices of the first embodiment are connected.

  A second platen 10 ′ is connected to the platen 10. The platen 10 ′ is divided into two areas, an area A ′ and an area B ′, and corresponds to the area A and the area B in the platen 10, respectively. A laser interferometer 20a 'is fixedly arranged on the side along the Y axis of the platen 10', and a laser interferometer 20b 'is fixed on the side along the X axis.

  A slider 1 is mounted on the platen 10, and a slider 1 'is mounted on the platen 10'. The positions of the sliders 1 and 1 'are individually controlled. These sliders move both on the platen 10 and on the platen 10 ', respectively. When these sliders are located in the area A, their positions are detected by the laser interferometers 20a and 20b, and when they are located in the area A ', their positions are detected by the laser interferometers 20a' and 20b '. It should be noted that bar mirrors are mounted on both side surfaces along the Y axis so that the sliders 1 and 1 'can detect the position in the X-axis direction with both laser interferometers 20a and 20a'. Has been. Other configurations are the same as those of the first embodiment.

  As an application example of the positioning apparatus of this embodiment, there is an exposure apparatus for manufacturing a semiconductor. An alignment device is provided above the area A for relative alignment between an electronic circuit pattern such as an IC formed on the reticle surface and the wafer, and an exposure device is provided above the area A ′. . A wafer is mounted on the slider 1 and is first positioned in the area A for alignment. Thereafter, the slider 1 is moved to the area A ′, and the wafer is exposed. While exposure is performed by the slider 1, the slider 1 'is positioned in the area A to perform alignment. When the exposure of the slider 1 is completed, the positions of the sliders 1 and 1 'are changed. In this way, the sliders are alternately reciprocated in the area A and the area A ′, and the alignment and exposure are alternately repeated. Thereby, the wafer processing throughput per unit time of the exposure apparatus can be increased.

It is explanatory drawing of the operation principle of the position detection by a resolver. It is a figure which shows the structure of a resolver. It is a top view which shows Example 1 of this invention. FIG. 3 is a diagram showing area division of the platen 10. It is a block diagram which shows the detail of the positioning device of Example 1. FIG. It is a figure which shows the change of the value of each signal at the time of switching of a position detection apparatus. 2 is an enlarged view of a tooth 10a of a platen 10. FIG. It is a figure which shows the position detection error Ea. 1 is a diagram showing a platen 10. FIG. It is a figure which shows the position detection error Eb. It is a top view which shows Example 2 of this invention. It is a top view which shows Example 3 of this invention. It is a block diagram which shows an example of the positioning device of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Slider 10 Platen 20, 20a, 20b Laser interferometer 21a, 21b Bar mirror 30, 30a-30c Resolver 100 Calculation part 100a, 100b Measurement processing part 100c Changeover switch 100d Coordinate establishment part 100e Correction part 101 Position command value generation part 102 Position control Part

Claims (6)

In a positioning apparatus comprising a slider whose position is controlled, and a platen in which magnetic pole teeth are formed on a surface facing the slider and the slider and a flat motor are configured.
A first position detecting device for detecting the position of the slider;
A second position detection device that detects the position of the slider in a specific area of the platen with higher accuracy than the first position detection device;
Switching means for selecting either the first or second position detecting device according to the position of the slider;
A position control unit that performs position control of the slider based on a position command value and a position detection value detected by a position detection device selected by the switching means;
A positioning device comprising:   The positioning apparatus according to claim 1, further comprising a correction unit that performs correction to maintain the slider at the same position before and after switching between the first and second position detection devices.   The correction unit detects the position command value and the position detection value detected by the second position detection device based on a detection error of the first position detection device when the switching unit switches the position detection device. The positioning device according to claim 2, wherein:   4. The positioning device according to claim 3, wherein the detection error of the first position detection device is a detection error specific to a tooth corresponding to a current position of the slider of the platen.   The positioning apparatus according to claim 3, wherein the detection error of the first position detection apparatus is a detection error that appears in synchronization with a tooth pitch of the platen. The first position detection device is a resolver provided in the slider,
The positioning apparatus according to claim 1, wherein the second position detection device is a laser interferometer.