JPH04314106A - Positioning device - Google Patents

Abstract

PURPOSE:To realize highly precise positioning without being affected by the restriction of the position detecting precision of a laser length measuring system. CONSTITUTION:A very small displacement element 4 to be moved slightly, a coarse adjusting mechanism to move this very small displacement element, a position detecting means 8, 9, 13 to measure the moved position of the very small displacement element, an open-loop control means 20, 17 to move slightly the very small displacement element toward a target position, and a coarse feedback control means 17 which receives the displacement position of the very small displacement element fed back from the position detecting means, and besides, adjusts coarsely the coarse adjusting mechanism as interlocking it with the very small displacement of the very small displacement element are provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning device using coarse and fine movements.

0002

2. Description of the Related Art FIG. 7 is a block diagram of such a positioning device. A slider 2 is slidably supported on a table 1 by a hydrostatic bearing 3. The slider 2 is provided with a piezoelectric element 4 and a mirror 5. Further, this slider 2 is connected to a moving rod 7 of a coarse movement mechanism 6. Note that a mirror 4 is located at the displacement position of the piezoelectric element 4.
A is provided.

On the other hand, a laser oscillator 8 is provided on the table 1, and each laser interferometer 9, 10, a beam splitter 11, and a mirror 12 are provided.
The laser beam output from the laser beam is split into two directions by the beam splitter 11, and one of the branched laser beams passes through the laser interferometer 9, is reflected by the mirror 5, and enters the laser interferometer 9 again. There is. Also, the other branched laser beam split by the beam splitter 11 is sent to the mirror 12.
The light is reflected by the laser interferometer 10, passes through the laser interferometer 10, is reflected by the mirror 4a, and enters the laser interferometer 10 again. The interference outputs of these laser interferometers 9 and 10 are transmitted to receivers 13 and 10, respectively.
14, the signals are converted into electrical signals and sent to the position control device 15.

The position control device 15 performs coarse movement and fine movement control. That is, the coarse movement control function of the position control device 15 determines the position of the mirror 5, that is, the position of the stage 2, from the electrical signal from the receiver 13, calculates the deviation between this position and the target position, and performs coarse movement according to this deviation. Send control signals. This coarse movement control signal is sent to a coarse movement drive circuit 16, and this coarse movement drive circuit 16 drives the coarse movement mechanism 6 in accordance with the coarse movement control signal.

Further, the fine movement control function of the position control device 15 determines the position of the mirror 4a, that is, the displacement position of the piezoelectric element 4, from the electric signal from the receiver 14, determines the deviation between this position and the target position, and calculates the deviation between this position and the target position. Sends a corresponding fine movement control signal. This fine movement control signal is sent to the fine movement drive circuit 17, and this fine movement drive circuit 17 drives the piezoelectric element 4 according to the fine movement control signal.
Apply voltage to.

However, in the above positioning, both the coarse movement and fine movement controls form a feedback system. For this reason, since a laser length measurement system consisting of a laser oscillator 8, laser interferometers 9 and 10, and receivers 13 and 14 is used as a feedback sensor for both fine movement control and coarse movement control, the displacement position of the piezoelectric element 4 is Final positioning is limited by the position detection accuracy of the laser length measurement system.

[0007]

As described above, the final positioning of the displacement position of the piezoelectric element 4 is limited by the position detection accuracy of the laser length measurement system. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a positioning device that can perform highly accurate positioning without being limited by the position detection accuracy of a laser length measurement system.

[0008]

[Means for Solving the Problems] The present invention provides a minute displacement element that makes a minute displacement, a coarse movement mechanism that moves the minute displacement element, a position detection means that measures the displacement position of the minute displacement element, and a minute displacement element that moves the minute displacement element. A positioning device that attempts to achieve the above object by comprising open-loop control means for slightly displacing the micro-displacement element toward a target position, and coarse-motion feedback control means for coarsely moving a coarse-motion mechanism in conjunction with the minute displacement of the micro-displacement element. It is.

[0009]

[Operation] By providing such a means, the minute displacement element is minutely displaced toward the target position by the open loop control means, and the displacement position of this minute displacement element is measured by the position detection means to determine this displacement position. The coarse movement feedback control means coarsely moves the coarse movement mechanism in conjunction with the minute displacement of the minute displacement element.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Note that the same parts as in FIG. 7 are given the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 1 is a block diagram of the positioning device, and FIG.
is a configuration diagram of an electric circuit. A piezoelectric element 4 is provided on the slider 2. This piezoelectric element 4 is a fine movement drive circuit 1
It undergoes minute displacement according to the voltage applied from 7.

On the other hand, the output terminal of the receiver 13 is connected to a fine/coarse movement control circuit 20 . This fine and coarse movement control circuit 20 has a coarse movement control function and a fine movement control function. The coarse movement control function uses electrical signals from the receiver 13 to control the mirror 4.
It has a function of determining the position a, that is, the displacement position of the piezoelectric element 4, determining the deviation between this position and the target position, and sending out a coarse movement control signal according to this deviation. In addition, the fine movement control function applies a voltage that causes the piezoelectric element 4 to contract by the amount of movement of the slider 2 when the slider 2 is moving, and compresses the piezoelectric element 4 by a minute distance when the slider 2 is stopped. It has a function of sending out a fine movement control signal for displacement. Therefore, the coarse movement control function forms a feedback control system, and the fine movement control function forms an open loop control system.

The coarse movement drive circuit 16 is a fine movement coarse movement control circuit 20.
It has a function of operating the coarse movement mechanism 6 in response to a coarse movement control signal from the compensation circuit 16a, as shown in FIG.
The D/A converter 16b, the PWM control circuit 16c, and the amplifier 16d are connected in series.

The fine movement drive circuit 17 is a fine movement coarse movement control circuit 20.
It has a function of applying voltage to the piezoelectric element 4 according to a fine movement control signal from the piezoelectric element 4, and has a configuration in which a D/A converter 17a and an amplifier 17b are connected in series.

Next, the voltage applied to the piezoelectric element 4 will be explained. Figure 3 shows the displacement characteristics of the piezoelectric element 4 with respect to the applied voltage.
Hysteresis occurs as shown in . However, the hysteresis in the minute displacement region A is small. For example, if the applied voltage Vs causes a minute displacement of 5 nm in the piezoelectric element 4 as shown in FIG. 4, the error due to hysteresis is 0.
It falls within the range of 3 nm. When positioning is on the order of negligible within this range of 0.3 nm, there is almost no influence of errors due to hysteresis. Therefore, the fine and coarse movement control circuit 2
The fine movement control function of 0 is 1 step for piezoelectric element 4 2
．． Sends a fine movement control signal with a displacement of 5 nm or less. Note that the coarse movement mechanism 6 and the laser oscillator 8 are operationally controlled by a computer 21. Next, the operation of the apparatus configured as described above will be explained.

For example, the fine movement control function of the fine and coarse movement control circuit 20 sends out a fine movement control signal that displaces the piezoelectric element 4 by 1 nm. In this case, if the piezoelectric element 4 has a displacement characteristic of 1 nm/10 V, a fine movement control signal is sent to apply a voltage of 10 V to the piezoelectric element 4 to displace it by 1 nm. This fine movement control signal is sent to the fine movement drive circuit 17, and this fine movement drive circuit 17 applies a voltage Vs to the piezoelectric element 4 according to a displacement of 1 nm. By applying this voltage, the piezoelectric element 4 is displaced by 1 nm in one step, as shown in FIG. Again, the fine movement control function sends out a fine movement control signal to further displace the piezoelectric element 4 by 1 nm in the next step, that is, a fine movement control signal to displace it by 2 nm. Hereinafter, similarly, the fine movement control function controls the piezoelectric element 4 to 1.
A fine movement control signal for displacing by 1 nm in steps is sent in 5 steps. Therefore, the piezoelectric element 4 has a thickness of 5 nm in 5 steps.
At this time, a voltage of 50V is applied to the piezoelectric element 4.

The fine movement control function of the fine and coarse movement control circuit 20 sets the voltage applied to the piezoelectric element 4 to "0" when the piezoelectric element 4 is displaced by 5 nm, and at the same time, the coarse movement control function of the fine and coarse movement control circuit 20 A coarse movement control signal is sent to displace the slider 2 by 5 nm. In this way, the slider 2 is displaced by 5 nm by the coarse movement mechanism 6.

[0018] Thereafter, the fine movement control and coarse movement control are similarly linked, and the piezoelectric element 4 is displaced by 1 nm per step by coarse movement control, then 5 nm in 5 steps, and then by 5 nm by coarse movement control. When the displacement position of the piezoelectric element 4 reaches the target position in this way, the positioning control ends.

As described above, in the above embodiment, the piezoelectric element 4 is minutely displaced toward the target position by open loop control, and the coarse movement mechanism 6 is coarsely moved in conjunction with the minute displacement of the piezoelectric element 4. Therefore, when one step of the piezoelectric element 4 is 1 nm and coarse and fine movements are made every 5 steps, the hysteresis is 0.3 nm as described above, and the positioning accuracy of the piezoelectric element 4 is set to 1 nm in an open loop.
Can be ordered. In this case, it is not affected by the measurement limitations of the laser length measurement system. Moreover, it is not affected by the hysteresis of the piezoelectric element 4. Therefore, the displacement characteristics of the piezoelectric element 4 can be used effectively and positioning can be performed with high precision.

It should be noted that the present invention is not limited to the above-mentioned embodiment, and may be modified without changing the gist thereof. For example, an electrostrictive element, a magnetostrictive element, etc. may be used in place of the piezoelectric element, and a linear scale may be used in place of the laser length measurement system. Further, if a piezoelectric element without hysteresis is used, even more accurate positioning can be achieved.

[0021]

As described in detail above, according to the present invention, it is possible to provide a positioning device that can perform highly accurate positioning without being limited by the position detection accuracy of a laser length measurement system.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a positioning device according to the present invention.

FIG. 2 is a circuit configuration diagram of the device.

FIG. 3 is a displacement characteristic diagram of a piezoelectric element in the same device.

FIG. 4 is a displacement characteristic diagram in the low voltage region of the piezoelectric element in the same device.

FIG. 5 is a diagram showing displacement due to fine movement and coarse movement in the same device.

FIG. 6 is a diagram showing the interlocking of fine movement and coarse movement in the same device.

FIG. 7 is a configuration diagram of a conventional device.

[Explanation of symbols]

2...Slider, 4...Piezoelectric element, 6...Coarse movement mechanism, 8...Laser oscillator, 9...Laser interferometer, 13...Receiver, 16...
Coarse movement drive circuit, 17... Fine movement drive circuit, 20... Fine movement coarse movement control circuit.

Claims (1)

[Claims] 1. A minute displacement element that makes a minute displacement, a coarse movement mechanism that moves the minute displacement element, a position detection means that measures a displacement position of the minute displacement element, and a position detecting means that moves the minute displacement element toward a target position. 1. A positioning device comprising: open loop control means for making a minute displacement; and coarse movement feedback control means for coarsely moving the coarse movement mechanism in conjunction with the minute displacement of the minute displacement element.