JPH074730B2 - Positioning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a highly accurate positioning device required in a machine tool, a semiconductor manufacturing apparatus or the like.

[Background of the Invention]

2. Description of the Related Art In recent years, in machine tools, finer and highly accurate positioning is required as the precision of machined parts increases. Further, in semiconductor manufacturing equipment, especially in mask aligners and the like, highly accurate positioning is required as the density of semiconductor elements increases.

[Conventional technology and problems]

Conventionally, in the case of performing highly accurate and fine positioning, a method of detecting the position of a positioning target and feeding it back to a control device is used. A glass scale, a laser length measuring device, a holographic scale, or the like is used as a detector for detecting the position of a positioning target. Since the scale of the glass scale cannot reduce the interval between graduation lines, usually only a resolution of about 1 μm can be obtained. Even if the electric division is performed, the resolution is only about 0.1 μm.

Further, the laser length measuring device can obtain a resolution of 0.01 μm, but it is expensive, and care must be taken so that the optical path of the laser is sealed or the optical path is not temporarily blocked by chips or the like. Moreover, there is a problem with the size of the light source, so it cannot be used easily.

The holographic scale can obtain a resolution of 0.01 μm, but it requires a laser light source and is expensive.

Further, these length-measuring devices have a problem that the maximum moving speed is limited due to electrical restrictions when trying to obtain high resolution.

On the other hand, the displacement meter can increase the resolution, but it cannot take a large measurement range.

[Object of the Invention]

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a positioning device that performs high-speed and high-resolution positioning by combining a linear scale and a displacement gauge.

[Structure of Invention]

In order to achieve the above-mentioned object, the present invention achieves high accuracy by moving a scale head of a linear scale by a small amount to perform positioning above the resolution of the linear scale and by feeding back the movement of the scale head by a displacement meter. It is characterized by performing positioning.

〔Example〕

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

The figure shows a positioning device according to an embodiment of the invention.

A guide surface 2 is formed on the device body 1, and a table 3
Is supported by the main body 1 and constrained by the guide surface 2 to move. A scale 4 is fixed to the table 3 to detect the position of the table 3. The scale head 5 is the main body 1
Static pressure pads 7 to 12 formed on the support member 6 fixed to the
Is fixed to the head holding base 13 which is held under static pressure. The head holder 13 moves a minute amount in the movement direction of the table 3, and the displacement amount is detected by the displacement meter 14.

The position of the table 3 is controlled by the controller 15. The table 3 is fed by a motor 16 driven by a command from the controller 15 and a feed screw and a nut (not shown).

Further, the servo amplifier 17 increases the difference between the command value from the controller 15 which is less than the scale resolution and the displacement gauge 14 to drive the servo valve 18 to adjust the supply pressure to the static pressure pads 7 and 8 to adjust the head holding base 13. Displace.

Next, the operation will be described.

When the table 3 is moved, the controller 15 drives the motor 16 above the scale resolution, and gives a command to the servo amplifier below the scale resolution to move the head holder 13.

First, the motor 16 is driven by the controller 15, and the table 3 is driven. The movement of the table 3 is detected by the scale 4 and the scale head 5 and fed back to the controller 15. Table 3 is always the controller
It is driven so that it becomes the same as the command value above the scale resolution from 15. Therefore, even after the command value from the controller 15 equal to or greater than the scale resolution and the movement amount of the table 3 match, the table 3 is displaced by an external force or the like,
When the movement amount of the table 3 deviates from the command value, the movement amount of the table 3 is fed back to the controller 15, so that the table 3 is returned to the original state.

On the other hand, for values below the scale resolution, the servo amplifier 17
Is output from the controller 15 as a command value less than the scale resolution. The servo amplifier 17 increases the difference between the command value below the scale resolution from the controller 15 and the output of the displacement gauge 14 and outputs it to the servo valve 18. The servo valve 18 distributes the supply pressure P _{S so} that the supply pressure to the static pressure pads 7 and 8 becomes a differential pressure proportional to the output of the servo amplifier 17. Head holder
13 moves to the side of the static pressure pads 7 and 8 that has decreased in pressure. The amount of movement of the head holder 13 is detected by the displacement gauge 14 and fed back to the servo amplifier 17. When the command value below the scale resolution from the controller 15 and the output of the displacement gauge 14 match and the difference becomes 0, the pressures of the static pressure pads 7 and 8 are balanced and the head holding table 13 completes the movement. For example, after the command value of the scale resolution or more from the controller 15 and the movement amount of the table 3 match, the controller 15
When the head holder 13 is moved by a command value from the scale resolution 15 or less, the scale head 5 fixed to the head holder 13 also moves. Then, as the scale head 5 moves, a displacement occurs in the relative distance between the scale 4 and the scale head 5, causing a difference between the command value from the controller 15 which is equal to or larger than the scale resolution and the movement amount of the table 3. The movement amount of the table 3 is fed back to the controller 15, and the table 3 is fed until the command value from the controller 15 which is equal to or larger than the scale resolution and the movement amount of the table 3 match.
As a result, Table 3 is moved by a small amount by the command value less than the scale resolution.

In the embodiment, oil is used as the pressure fluid, but gas such as air can be used. When gas is used as the fluid, the same function can be satisfied with the same configuration.

It is also possible to use a piezo element to move the scale head.

As described above, in the embodiment of the present invention, by slightly moving the scale head, it is possible to perform minute positioning below the resolution of the scale.

〔The invention's effect〕

As described above, according to the present invention, since the scale head is moved in the table movement direction by the commanded amount, and thereafter the motor for driving the table is moved by the movement amount of the scale head, it is less than the scale resolution. The positioning resolution can be obtained, and even if the resolution is further increased, the frequency of the feedback signal from the scale is the same as before it is increased, so that high-speed positioning can be performed.

[Brief description of drawings]

The figure is a block diagram of a positioning device according to an embodiment of the present invention. 3 ... table, 4 ... scale, 5 ... scale head, 13 ... head holder, 14 ... displacement meter, 15 ... controller, 17 ... servo amplifier, 18 ... servo valve.

Claims (1)

[Claims] 1. A moving body driven along a guide surface formed in a main body of the apparatus, a motor for driving the moving body, a scale fixed to the moving body, and a scale fixed to the main body. Support member, a head holding base statically supported by the supporting member, a scale head fixed to the head holding base, and a position signal of the moving body taken out by the scale head from the scale A controller for controlling the position via the motor, a displacement meter fixed to the support member, for measuring the displacement in the moving direction of the moving body with respect to the support member of the head holding base,
A servo amplifier for increasing the difference between the control signal having a scale resolution equal to or less than the servo valve output from the controller and the output of the displacement gauge; and a static pressure pocket formed on a support member for holding the head holding base at a static pressure, The controller comprises a servo valve that distributes the supply pressure to the static pressure pocket so that the difference signal of the servo amplifier becomes zero, and the controller moves the moving body via the motor by a position signal from the scale head having a scale resolution or higher. The position of the moving body is controlled through the motor in order to eliminate the positional deviation of the scale and scale head which is less than the resolution of the scale head, and further, the servo amplifier and the servo valve are controlled. By controlling the movement of the head holding table below the scale resolution via the static pressure pocket and Positioning device, characterized in that the above scale head is only moved relative following scale resolution.