JPS6039213A - Precision positioning device - Google Patents

Abstract

PURPOSE:To exercise positioning control with high precision and high resolving power by revising stepwise a control variable to a mechanical movement system being an object to be controlled so as to converge stepwise the actual position of the mechanical movement system to an object position. CONSTITUTION:A position detector 22 like a laser range finder gives a position detecting value Dx to a comparator circuit 24 from a mechanical displacement of the mechanical movement system 20 such as an XY plotter, a difference data DELTAX between the Dx and an object value Dp and a code signal Sx are detected 26, and the result is fed to a register 32 via an adder/subtractor circuit 28. Further, the value stored in the register 32 is revised intermittently at each period of a clock phi of a clock generating circuit 30, its output is fed back to the circuit 28, where the output is added. After its output signal is D/A-converted (34), the result output drives (36) a piezoelectric element 40 so as to drive mechanically the mechanical movement system 20.

Description

[Detailed Description of the Invention] [Technical Field] This invention relates to a technology that is particularly effective when applied to control technology and precise positioning, for example, a technology that is particularly effective when applied to precise positioning on an XY table. It is something.

[Background technology]

The present inventor has developed the following technology regarding control technology, particularly precision positioning technology for mechanical motion systems.

In other words, the electric power that drives the mechanical motion system that is the object of control
The apparatus comprises a mechanical conversion means and a position detection means for detecting mechanical displacement of the mechanical movement system, and drives the electric-mechanical conversion means based on the difference between a detected value of the position detection means and a target value. It is. This will be explained in more detail below.

First, FIG. 1 shows an example of a positioning device. In the device shown in the figure, a type of control feedback loop is formed in which a mechanical movement system such as an XY table is controlled, and thereby the position of the XY table is accurately guided to a target position. It is.

In FIG. 1, first, a motor M drives an XY table as a mechanical movement system in the X-axis direction and the Y-axis direction.

This motor M corresponds to the above-mentioned electrical/mechanical conversion means. The distance driven by the motor M is detected by a position detector EC consisting of a rotary encoder. This detected value DB is compared with a set value Ps by the movement distance setting means 10.

The set value Ps corresponds to the target value described above. The moving distance setting means 10 outputs the difference VO between the set value P8 and the detected value D8. This difference Vo is input to the difference detection means 12 as a reference value. The difference detection means 12 detects the difference (VoVs) between the reference value (Vo) and the detected rotational speed value v8 of the motor M. The detected rotational speed value v8 is detected by a speed detector TG connected to the motor M. The above difference (Vo-v
s) is amplified by the servo amplifier 14 and becomes the driving level of the motor M. As a result, the motor M has a set value P
8 and the detected value Ds. As a result, the XY table to be controlled is positioned at a predetermined target position.

1 - In such technology, the set value Ps and the detected value D
Since the difference between
The inventor has found that a problem arises in that it becomes very difficult to perform stable control. Particularly in the field of highly accurate positioning, which requires a high resolution of 0.01 .mu.m, overshoot or hunting phenomena are very likely to occur due to excessive control.

[Purpose of the invention]

An object of the present invention is to provide a technique that enables highly accurate positioning.

Another object of the invention is to provide a high resolution positioning technique.

Another object of the present invention is to provide a control technique that allows stable positioning with high precision and high resolution.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, by updating the control amount for the mechanical motion system that is the controlled object in stages, the actual position of the mechanical motion system is gradually converged to the target position2, thereby achieving high-precision and high-resolution positioning. This achieves the purpose of stably performing control.

〔Example〕

Hereinafter, typical embodiments of the present invention will be described with reference to the drawings.

In addition, the same or corresponding parts are indicated by the same reference numerals in the drawings.

FIG. 2 shows an embodiment of a precision positioning device according to the present invention.

First, the positioning device shown in the figure is provided with an electrical φ mechanical conversion means for driving a mechanical movement system to be controlled, and a position detection means for detecting mechanical displacement of the mechanical movement system. Then, the detected value Dx of the position detecting means
The electric/mechanical conversion means is configured to be driven based on the difference between the target value Dp and the target value Dp.

It also has a calculation means which uses the difference ΔX1 between the detection value Dx of the position detection means and the target value Dp as one addition input, and a storage means which temporarily holds the output of this calculation means. Then, the electric/mechanical conversion means is driven based on the contents held in the storage means. At the same time, the content temporarily held in the storage means is used as the other addition input of the calculation means.

To explain FIG. 2 in detail, first, there are 20 mechanical motion systems to be controlled, such as an XY table.

Reference numeral 22 denotes a position detecting means for detecting mechanical displacement of the mechanical movement system, and is, for example, a laser length measuring device.

This length measuring device 22 is configured to output the detected position value Dx as digital data.

24 is the position detection value Dx and target value Dp by the position detection means
The means for detecting and outputting the difference data ΔX is a beam, for example, a digital data comparison circuit.

26 is a difference detection circuit, which is connected to the digital comparison circuit 24.
Based on the difference data △X and the direction detection signal Sx output from the
-Dx). This difference value ΔX1 is digital data, and is between the position detection value Dx and the target value D.
It is based on the difference from p. However, since the digital data (difference value ΔXi) is signed, it also includes information regarding the direction of whether or not the detected value Dx is larger than the set value Dp.

Reference numeral 28 denotes an arithmetic means which inputs the difference value ΔX1f as one addition input, and is, for example, a digital addition/subtraction circuit.

Reference numeral 30 denotes a means for continuously operating the addition/subtraction circuit 28 at a predetermined period, and is, for example, a clock generation circuit. This circuit 30 is configured such that the period of its output black-nokuda can be adjusted arbitrarily.

This output clock y becomes the operation control clock for the addition/subtraction circuit 28.

32 is a storage means for temporarily holding the output (ΔX1+ΔX2) of the arithmetic means, and is, for example, a parallel register.

34 is the content temporarily held in the storage means (△X2:△
X2=ΔX1+ΔX2) into an analog value, and is, for example, a D/A converter (digital/analog converter).

36 is means for driving the electrical/mechanical conversion means based on the content (ΔX2) temporarily held in the storage means,
For example, a high voltage output circuit. This circuit 36 includes a gain adjuster 38. Thereby, the magnitude of the control amount for the electrical/mechanical conversion means can be variably adjusted as desired.

Reference numeral 40 denotes an electrical/mechanical conversion means for driving the mechanical motion system to be controlled, and is, for example, a piezo element. This piezo element 40 is driven by the output of the high voltage output circuit 34. Then, the elastic deformation caused by the piezoelectric effect caused by the drive minutely drives the XY table 20.

Here, the contents temporarily held in the register 32 (
ΔX2: ΔX2=ΔX1+ΔX2) becomes the other addition input of the addition/subtraction circuit 28. This addition/subtraction circuit 28 is
It operates intermittently depending on the cycle of the cloffish mentioned above. Therefore, the contents (ΔX2) held in the register 32 are updated intermittently at each cycle of the clock. In other words, the value (△X1 + △X2) obtained by adding the difference value △X1 newly output from the difference detection circuit 26 to the value (△X2) held in the register 32 is obtained every cycle of the cloffish. Then, the data is newly held in the register 32. Then, the contents held in the register 32 (△X1+△X2
) is applied to the piezo element 40 via the D/A converter 34 and the high voltage output circuit 36. As a result, the piezo element 40
As illustrated in FIG. 3, the drive voltage Vx applied to the clock is updated in stages at each clock cycle. The piezo element 40 then receives a voltage Vx that is updated in stages.
As a result, the XY table 20 is driven, and the detected value Dx at that position gradually converges to the target value Dp. I'll go.

What should be noted here is that the drive voltage Vx applied to the piezo element 40, that is, the control amount is the position detection value Dx
This means that it is not directly determined from the difference between the target value Dp and the target value Dp, but is determined based on the previous control amount and control result. That is, a certain control amount is once applied, and the displacement of the XY table 40 due to this is detected after a certain period of time. If the displacement does not reach the target after a certain period of time, that is, if the controlled amount is insufficient, the controlled amount corresponding to the shortage is added to the previously given controlled amount, and this is applied to the next be the control amount. Then, the displacement of the KXY table 40 is checked again after a certain period of time.

If the control amount is still insufficient, the insufficient amount is further added and the same process is repeated. By repeating this process every cycle of the cloffish, the optimal control amount can be set step by step. As a result, positioning control with high precision and high resolution can be performed very stably without suddenly applying a large control amount from the beginning and causing overshoot or hunting.

For this reason, it is desirable that the cycle of the clock end and the gain of the high voltage output circuit 36 be configured to be variably adjustable. The period of the chronograph blowfish is set according to the mechanical response speed of the XY table 20 that is the controlled object. Further, the gain is set so that the control amount does not become excessive, that is, so that it can quickly stabilize to the optimum control amount after changing in several stages.

〔effect〕

(1) By changing the control amount in stages, it is possible to obtain optimal control conditions and to stably perform highly accurate control.

(2) By adding the control amount in stages, it is possible to obtain appropriate control conditions and significantly improve control resolution.

(3) By adopting a configuration in which no feed bank is applied up to a certain finite amount, position determination on the order of 0.01 μm can be performed with high precision.

The above (1) and (2) provide a synergistic effect in that stable positioning control without overshoot or hunting is performed with higher accuracy and resolution.

Although the invention made by the present inventor has been specifically explained above using examples, this invention is not limited to the above-mentioned examples, and it is understood that various changes can be made without departing from the gist of the invention. Needless to say. For example, the piezo element may be a magnetostrictive element or an electromagnetic solenoid. Further, the comparison circuit, difference detection circuit, addition/subtraction circuit, etc. can be easily substituted by using a microcomputer.

[Application field]

In the above explanation, the control technology applied to the positioning of an XY table, which is the field of application behind the invention made by the present inventor, has been mainly explained, but it is not limited thereto. It can also be applied to machine control technology with three or more axes. It can be applied at least to conditions where the displacement of a mechanical motion system is electrically controlled.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a positioning device other than the present invention, FIG. 2 is a block diagram showing an embodiment of a precision positioning device according to the present invention, and FIG. 3 is the device shown in FIG. 2. 3 is a timing chart showing the amount of operation. 10... Movement distance setting means, 12... Difference detection means,
14... Servo amplifier, M... Motor, TG...
Speed detector, EC...Position detector, Ps...Set value,
D8...Position detection value, ■8...Speed detection value, 20.
... Mechanical motion system (XY table), 22... Laser length measuring device (position detection means), 24... Comparison circuit, 26.
...Difference detection circuit, 28... Arithmetic means (addition/subtraction circuit),
30... Clock generation circuit, 32... Storage means (register), 34... D/A converter, 36... High voltage output circuit, 38... Gain adjuster, 40... Electricity Fist mechanical conversion means (piezo element), Dx...Position detection value, D
p...Target value, △X...Difference data, Sx...Direction detection signal, △X1...Difference value, △X2...Temporarily held value (addition output), G.・Clock, Vx・
...High driving voltage. Figure 1 Figure 2

Claims (1)

[Claims] 1. An electrical-mechanical conversion means for driving a mechanical movement system to be controlled, and a position detection means for detecting mechanical displacement of the mechanical movement system, and a detection value of the position detection means is provided. and a target value, the precision positioning device is configured to drive the electric/mechanical conversion means based on the difference between the position detection means and the target value, and the difference between the detection value of the position detection means and the target value is used as one additional force. It has a calculation means and a storage means for temporarily retaining the output of the calculation means, and drives the electrical/mechanical conversion means based on the contents stored in the storage means, and also stores information in the storage means. A precision positioning device in which the content held in the above is used as an addition input to the other calculation means. 2. The precision positioning device according to claim 1, wherein the electrical/mechanical conversion means is a piezo element. 3. Claim 1 or 2, characterized in that the operation of the calculation means is performed intermittently.
Precision positioning device as described in section.