JP2001322045A - Stage control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stage control device which suppresses the unbalance of the compensation of the self-weight of a mobile stage, lighten the load of a drive device used in controlling the position, suppresses the heat generation and reduces the size of the device, and improves the stability and the accuracy of the device. SOLUTION: The stage control device comprises the mobile stage 103 supported via a bearing pad 102(a), etc., and movable in the direction of the gravity; a position control compensator 108, etc., for controlling the positioning of the mobile state 103 in the direction of the gravity by the feedback control; a non-contact cylinder 111, etc., for compensating the gravity on the mobile stage 103; a laser beam distance measuring instrument 107 for detecting the position of the mobile stage 103; and a pressure command correcting means 116 for correcting the pressure command for compensating the gravity based on the target position signal set by the position command means 109 or the position signal detected by the laser beam distance measuring instrument 107.

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 position of a moving stage which moves in the direction of gravity of a precision machine such as a cutting machine, a grinding machine, a polishing machine or the like which requires precise precision. .

[0002]

2. Description of the Related Art Conventionally, as a configuration of a control device for a moving stage that moves in the direction of gravity, there is one shown in FIG. The control device in FIG. 5 includes a position control unit for controlling the positioning of the moving stage 502 and a pressure control unit for compensating the own weight of the moving stage 502, and performs independent control on the positioning and the compensation of the own weight.

A position control unit includes ball screws 504, 505 and a motor 503 for driving the moving stage 502, a length measuring device 507 for detecting the position of the moving stage 502, and position command means 509 for setting the position of the moving stage 502.
And the position of the moving stage 502 detected by the length measuring device 507 and the position command from the position command means 509 are compared and calculated.
And a position control compensator 508 that outputs a thrust command to the motor 503 via the motor driving device 510.

[0004] The pressure control unit includes a fluid cylinder 511 for generating a thrust for balancing the weight of the moving stage 502.
A pressure detector 512 for detecting the fluid pressure in the fluid cylinder 511; a pressure command means 516 for commanding a value by which the thrust by the fluid cylinder 511 is balanced with respect to the weight of the moving stage 502; The output of the pressure detector 512 is compared to calculate the fluid control valve drive 51
And a pressure control compensator 514 that outputs a control signal to the fluid control valve 513 via the control valve 5.

[0005]

In order to control the pressure control unit and the position control unit in an independent manner as in the conventional example shown in FIG. 5, the moving stage 502 is controlled by the fluid pressure controlled by the pressure control unit. Self-weight compensation must be stable. In the conventional example shown in FIG. 5, in order to perform stable self-weight compensation, a seal of the sliding portion of the fluid cylinder 511 is secured, and the pressure detected by the pressure detector 512 reflects the pressure in the fluid cylinder 511. Must be. However, in the fluid cylinder 511 in which such a seal is secured, friction occurs in the sliding portion, which causes deterioration in positioning accuracy.

In order to eliminate the friction of the sliding portion of the fluid cylinder 511 in order to improve the positioning accuracy, it is conceivable to use a non-contact cylinder having a bearing pad as shown in FIG. However, when a non-contact cylinder is used, a thrust imbalance occurs due to a thrust fluctuation caused by the pressure distribution in the cylinder as shown in FIG. Since the position control motor is responsible for the thrust corresponding to the unbalance, there is a problem that heat generated by the motor increases, and in some cases, the motor must be increased in size.

The present invention has been made in view of the above-mentioned problems of the conventional stage control device, and has been designed to suppress the imbalance of thrust for compensating the weight of the moving stage, reduce the load on a driving device such as a motor used for position control, An object of the present invention is to provide a stage control device capable of realizing suppression of heat generation and miniaturization of the device, and improving stability and accuracy of the device.

[0008]

SUMMARY OF THE INVENTION In order to solve the problems described in the prior art and achieve the above object, the present invention provides a moving stage supported by a fluid bearing and provided to be movable in the direction of gravity. A position control device for detecting a position of the moving stage in a stage control device including a positioning control device for performing positioning control of the moving stage in the direction of gravity by feedback control, and a gravity compensating device for compensating for gravity applied to the moving stage. Pressure correction means for correcting a pressure command for gravity compensation based on at least one of a target position signal set in the positioning control device and a position signal detected by the position detection means. It is characterized by.

In a preferred embodiment of the present invention, first,
A non-contact cylinder as shown in FIG. 2 is used to eliminate friction of the self-weight compensation fluid cylinder. At the same time, in the fluid pressure control of the non-contact cylinder, stable self-weight compensation and stable position control are realized by providing a pressure correction means for changing the control pressure according to the position of the moving stage. In addition, since the load on the motor in the position control is reduced by stable weight compensation, the size of the apparatus can be reduced.

[0010]

FIG. 1, FIG. 2, FIG. 3, and FIG.
It will be described according to. In FIG. 1, 101 is a guide for guiding a moving stage, 102 (a) and 102 (b) are fluid bearings attached to the moving stage, 103 is a moving stage, and 104 is a fixed linear motor for driving the moving stage 103. Reference numeral 105 denotes a movable element of a linear motor, reference numeral 106 denotes a target mirror of a laser length measuring device as a position detecting means, reference numeral 107 denotes a laser measuring device of a position detecting means,
08 is a position control compensator. This position control compensator 10
Reference numeral 8 denotes a PID compensator that generates a control signal from a position signal detected by a laser length measuring device 107 serving as a position detecting unit and a target position signal from a position instructing unit 109 for setting a target position of the moving stage 103. And a compensator. 109 is a position command means for setting a target position of the moving stage 103. 110 is a motor drive for amplifying a control signal from the position control compensator 108 to drive a linear motor 120 constituted by the stator 104 and the mover 105. Device, 111 is a moving stage 103
Non-contact cylinder that generates thrust to maintain its own weight
12 is a pressure detector for detecting the fluid pressure in the non-contact cylinder 111, 113 is a fluid control valve for controlling the compressed fluid supplied to the non-contact cylinder 111, and 114 is a pressure control compensator. The pressure control compensator 114 generates a pressure control signal from a pressure signal detected by the pressure detector 112 and a target pressure signal set by the pressure command means 117 and obtained through the pressure command correction means 116. Reference numeral 115 denotes a fluid control valve driving device that drives the fluid control valve 113 based on a pressure control signal from the pressure control compensator 114. Reference numeral 118 denotes a compressed fluid controlled by the fluid control valve 113, which is inside the non-contact cylinder 111. Supplied to

FIG. 2 is a diagram showing the configuration of the non-contact cylinder used in the present embodiment. In FIG. 2, reference numeral 201 denotes a cylinder rod constituting a cylinder, 202 denotes a cylinder body, 203 denotes a supply path for supplying a compressed fluid 214 to a bearing pad 204 provided on the cylinder rod 201, and 204 denotes an inner end of the cylinder rod 201. An annular fluid bearing pad provided on the outer circumference of the piston portion 211 for supporting the cylinder rod 201 from the cylinder body 202 in a non-contact manner, 205 is a pressure chamber in which compressed fluid supplied to the bearing pad 204 stays, 206 Is a supply port for supplying a compressed fluid (air) 212 to a bearing pad 207 provided on the cylinder body 202, and 207 is a circle provided on the cylinder body 202 for supporting the cylinder rod 201 from the cylinder body 202 in a non-contact manner. Ring-shaped fluid bearing pad, 208 is supplied to mail receiving pad 207 That the pressure chamber compressed fluid retention, 209 compressed fluid to generate a thrust in a non-contact cylinder 111 (Air) 21
A supply port 240 for supplying 3 is an open port for compressed fluid.

The target position signal set by the position command means 109 is compared and calculated by the position control compensator 108 with the position signal detected by the laser length measuring device 107, and a control signal such that the position signal becomes the target position signal. Generate The generated control signal is amplified by the motor driving device 110. In response to the amplified control signal, the linear motor 120 including the stator 104 and the mover 105 generates a thrust and moves the moving stage 103 to perform position control. When the moving stage 103 moves in the direction of gravity, a thrust for supporting the weight of the moving stage 103 must always be given to the moving stage 103. If the thrust is compensated for by the thrust generated by the linear motor 120, the linear motor 120 must be increased or the current flowing through the linear motor 120 must be increased. Therefore, a self-weight compensating device using a fluid cylinder different from the position control device that generates a thrust for supporting the weight of the moving stage 103 is provided.

The self-weight compensator according to the present embodiment comprises a pressure detector 112, a fluid control valve 113, a pressure control compensator 114,
Fluid control valve driving device 115 and pressure command correcting means 11
6 and the like.

In the self-weight compensator, the set pressure command signal is transmitted to the pressure detector 112 by the pressure control compensator 114.
Is compared with the detected pressure signal. The result is amplified by the fluid control valve drive 115 and the fluid control valve 1
13 is driven. A pressure control fluid 118 controlled by the fluid control valve 113 is supplied into the cylinder, and a thrust is given to the moving stage 103 by the non-contact cylinder 111.

However, when the fluid cylinder is a non-contact cylinder 111 having a structure as shown in FIG.
The pressure distribution shown in FIG. 3 is generated near the bearing pads 204 and 207 by the compressed fluid supplied from 02 to the bearing pads 204 and 207 for supporting the cylinder rod 201 in a non-contact manner.

In the case of the non-contact cylinder 111 having such a configuration, as shown in FIG. 3, even if the control pressure Ps supplied for giving the thrust by the non-contact cylinder 111 is constant, the thrust of the non-contact cylinder 111 is reduced. The contributing pressure Pt varies depending on a change in the capacity of the non-contact cylinder 111, that is, the position of the moving stage 103.

In order to suppress this fluctuation, the control pressure Ps is changed as shown in FIG. When the moving stage 103 moves from the state shown in FIG. 9A to the states shown in FIGS. 9B and 9C, the control pressure Ps of the non-contact cylinder 111 is changed in accordance with the movement. Thus, the fluid pressure Pt that contributes to the thrust generated in the non-contact cylinder 111 can be kept constant regardless of the position of the moving stage 103.

The stage control device according to the present embodiment, as shown in FIG. 1, performs a pressure command correction so that the control pressure Ps of the fluid supplied to the non-contact cylinder 111 can be changed depending on the position of the moving stage 103. A means 116 is provided to correct the set command pressure of the pressure command means 117 based on a position command signal to the moving stage 103 set by the position command means 107. This correction is performed by moving stage 103
The thrust of the non-contact cylinder 111 is kept constant by changing the control pressure of the non-contact cylinder for self-weight compensation depending on the position of the non-contact cylinder 111.

As a correction method, there is a method of calculating a command pressure for correction by calculating a linear expression using a ratio of numerical values representing the position of the moving stage 103 as a coefficient. That is, in FIG. 4, it is assumed that the command pressure at that time is Pa, and the numerical value representing the position of the moving stage 103 at that time is Xa, based on the moving stage position where the non-contact cylinder 111 is in the state (A). . If the numerical value representing the position of the moving stage 103 is Xc when the moving stage 103 moves and the non-contact cylinder 111 enters the state of (C), the command pressure Pc in this method is Pc = (Xa × Pa ) / Xc (where Xc> Xa).

As another method, the position of the moving stage 103 and the thrust of the non-contact cylinder 111 are measured in advance, and a correction data table coefficient for the pressure command is created from the measurement result. There is a method of calculating the pressure command value by referring to the correction data table coefficient every time the.

The moving stage 10 serving as a reference signal for correcting the target control pressure by the pressure command correcting means 116.
The same effect can be obtained by using the position signal of the laser length measuring device 107 as the position detecting means for the position information 3 instead of the above-mentioned position command signal.

[0022]

According to the present invention, the control pressure of the self-weight compensation cylinder is corrected according to the position of the moving stage, thereby suppressing the thrust fluctuation of the cylinder caused by the pressure distribution in the fluid cylinder chamber used for self-weight compensation. Unbalance of self-weight compensation can be suppressed. Therefore, the load on a driving device such as a motor used for position control can be reduced, and heat generation can be suppressed and the device can be downsized.

Further, when a non-contact cylinder having a structure that easily generates pressure distribution in the cylinder chamber is used, the imbalance of self-weight compensation by the fluid cylinder can be suppressed, and non-linear elements such as friction in position control can be eliminated. In addition, the stability and accuracy of the device can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a stage control device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a fluid cylinder for self-weight compensation according to an embodiment of the present invention.

FIG. 3 is a view for explaining an operation of the self-weight compensation fluid cylinder according to the embodiment of the present invention.

FIG. 4 is a diagram for explaining an embodiment of the present invention.

FIG. 5 is a configuration diagram illustrating an example of a conventional stage control device.

[Explanation of symbols]

101: guide, 102: bearing pad, 103: moving stage, 104: stator of linear motor, 105: mover of linear motor, 106: mirror, 107: laser measuring device, 108: position control compensator, 109: Position command means, 110: motor drive device, 111: non-contact cylinder, 112: pressure detector, 113: fluid control valve, 11
4: pressure control compensator, 115: fluid control valve drive, 1
16: pressure command correction means, 117: pressure command means, 11
8: controlled fluid, 120: linear motor, 201:
Cylinder rod, 202: cylinder body, 203: bearing fluid supply path, 204: bearing pad, 205: pressure chamber, 206: bearing fluid supply port, 207: bearing pad, 208: pressure chamber, 209: cylinder fluid supply mouth,
212, 213, 214: compressed fluid (air), 501:
Guide, 502: moving stage, 503: motor, 50
4,505: ball screw, 506: mirror, 507: laser measuring device, 508: position control compensator, 509: position command means, 510: motor drive device, 511: fluid cylinder, 512: pressure detector, 513: Fluid control valve, 51
4: pressure control compensator, 515: fluid control valve driving device, 5
16: pressure command means, 517: controlled fluid.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B23Q 1/30 1/14 B 1/18 Z

Claims (4)

[Claims] 1. A moving stage supported by a fluid bearing and movably provided in a gravitational direction, a positioning control device for positioning the moving stage in a gravitational direction by feedback control, and a gravitational force for compensating the gravitational force applied to the moving stage In a stage control device provided with a compensating device, a position detecting means for detecting a position of the moving stage is provided, and at least a target position signal set in the positioning control device and a position signal detected by the position detecting means. A stage control device comprising: a pressure correction unit that corrects a pressure command for gravity compensation based on one of them. 2. A fluid cylinder in the gravity compensating device, wherein a bearing pad is provided on a cylinder rod and a cylinder body, and a minute gap is formed between the cylinder body and the cylinder rod by compressed fluid supplied to the bearing pad. The stage control device according to claim 1, wherein the stage control device is a certain non-contact cylinder. 3. The stage according to claim 1, wherein the pressure command correction by the pressure command correction means is performed by calculating a linear expression using a ratio of a position of the moving stage as a coefficient. Control device. 4. The pressure command correction by the pressure command correction means is performed by a correction coefficient data table created from correlation data between the position of the moving stage and the thrust of the fluid cylinder measured in advance. The stage control device according to claim 1 or 2, wherein