JPS5892010A - Position control system - Google Patents

Abstract

PURPOSE:To converge a position into an objective position quickly, by providing a switch for an input and output each of an integrator and also a signal system initially setting a signal corresponding to an objective value to the integrator and a switch switching the signal system. CONSTITUTION:When an electrostriction element 1 is displaced and closes to an objective, a position deviation closes to 0. When the deviation is smaller than a set level, an output Sw of a switch changeover circuit 10 goes to 1, a switch 9 is opened and switches 6, 7 are closed. Thus, an integration system is also operative, but since a value in which an integration output I0 might be converged finally is preset to the integrator 5, the sum with a proportional component output P0 is almost the same value. Thus, a displacement signal V0 is smoothly converged into the objective value without overshooting and quick settling time can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a proportional operation l! The present invention relates to a position control method that precisely controls the position of a controlled object in a closed loop using an element, and more specifically, it uses an electrostrictive element used in lithography equipment in the semiconductor manufacturing process to perform positioning with an accuracy of 0.1 μm or more. This invention relates to a drive control method for a fine movement device.

Printing of circuit patterns in the semiconductor manufacturing process requires technology to precisely position and control samples such as wafers at n degrees of 0.1 μm or more using equipment. This is achieved by combining a coarse movement table driven by a screw feeding mechanism and a fine movement table that makes fine movements of several μm or less using an electrostrictive element or the like. As a drive source for the above-mentioned fine movement table, in addition to an electrostrictive element that expands and contracts in proportion to the drive electric field, an electromagnetic force actuator that displaces in proportion to the drive current, etc. is used. An example of a conventional configuration for performing closed-loop position control using these driving elements will be described with reference to FIG. The output displacement Xo of the electrostrictive element 1 is detected by the position detector 2 as a displacement signal Vo, and the difference from the target position signal V1 is calculated. If there is a difference between the two, the error signal is amplified by the proportional amplifier 3 having an appropriate amplification factor, and then the electrostrictive element 1 is moved through the drive circuit 41 in the direction where the above-mentioned error becomes smaller. Displace. This control method is a proportional control method, which causes a steady deviation, that is, a positioning error. Therefore, when f# precise positioning is required, an integrator 5 is added and a proportional integral control method is used. Although positioning accuracy is improved by adding an integral system as described above, on the contrary, it takes a long time to position 91, which has a slow response due to the phase lag of the integrator. In other words, when the target value ■1 changes in a stepwise manner at time T as shown in Figure 2 (Jl), the signal P proportional to one position deviation will be proportionally amplified *a as shown in Figure 2 (b). The saturation output level reaches 1.0, and the output I of the integrator 5
s % is integrated up to the saturation level 1.0 as shown in (C) of the same figure. The electrostrictive element 1 is driven by the sum of the above two signals and reaches the target value, but the integral output Io is determined by the displacement signal Vo at time T,
saturation level 1 only after passing the target value.
．． Since the output displacement Vo starts to decrease from 0, it goes far past the target value, then returns to the target value, and eventually converges to the target value in an oscillatory manner.As mentioned above, when the integrator 5 is included in the loop, the output displacement Vo reaches the target value. If the value suddenly changes, the integrator 5 once reaches the saturation level, and it takes time for the vibration to settle, which is probably a drawback of the conventional relative integral control system.

Therefore, an object of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods, and to provide a position control method that quickly converges to a target value even in a proportional-integral control system.

This invention will be explained in detail below using the embodiment shown in FIG. In this embodiment, the integral ii5 is compared to the conventional example shown in FIG.
A switch 6 and a switch 7 are provided on the input side and the output side, respectively, and furthermore, a signal system for initializing the target value vI is newly installed in the integral-5, and a switch 7 is provided in the middle to connect the signal on and off. ing. These three switches 6
．． 7 and 9 are opened and closed by the output signal Sv of the switch changeover circuit 10, and the switch 6 and the switch 7 are
The switch 9 is closed when the voltage is 1 m (p), and the switch 9 is closed when 8v="0#" due to the action of the signal inverter 11, contrary to the previous two.

The switch changeover circuit 10t is a comparison/judgment circuit which inputs the positional deviation signal and operates to set the output signal 8w to "1#" only when the magnitude of the 6pm positional deviation signal is smaller than a certain set novel.

In the control configuration described above, as shown in FIG.
When 11Vt changes stepwise, the position deviation signal V @
V + occurs, and the deviation proportional signal Pa reaches the saturation level 1.
0 at 1, and the electrostrictive element 1 is displaced via the driving circuit tIII4. At the same time as this activation, the position deviation signal is set at the setting level S of the switch changeover circuit 10! Since the output signal 8w becomes "0", the switch 6.7 is opened, while the switch 9 is closed, and the signal level corresponding to the target value V+ is sent to the integrator 5 (L5 is initialized). However, since the switch 7 is open, the integral output signal is 16, 0, and 11, as shown in Figure (b).In the end, the control system operates only by proportional control. So, differentiation circuit 1
1 detects the velocity component by differentiating the displacement output v0, and stabilizes the control system by checking the negative polarity.

generally well known.

Now, when the electrostrictive element 1 is displaced and approaches the target value.

When the positional deviation approaches 0 and becomes smaller than the above-mentioned set level S at time 1 T, the output Sv of the switch changeover circuit 10 becomes 112, and at the same time the L switch 9 is opened and the switch 6. - Close. As a result, the integral system also comes into operation, but as shown in Figure 44 (C), the integrator 5 has in advance set the integral output Io to Jth, which is the value 0.5 that will eventually be picked up. As a result, the sum with the proportional component output P0 becomes approximately 0.5, resulting in the displacement signal V as shown in FIG. 4(d).

converges to the target value smoothly without adding too much to the target value. As a result, a steady state can be reached much more quickly than in the conventional example shown in FIG.

In the above-described embodiment, the position deviation signal is used as the object of comparison and judgment by the switch changeover circuit 10.

Alternatively, the speed signal which is the output signal of the differentiating circuit 11 may be used, and when the magnitude of this signal is small, the output signal Sv may be set to 11'. Alternatively, it may be a logical sum of one and both wheels signals. In other words, these □ can be used depending on the type and purpose of the controlled object.

As can be seen from the above explanation, 1. In the case of a transient state such as a sudden change in the target value in a proportional-integral (which may also include a differential system) position control system, the integral system is separated from the control loop; By initially setting the value that the integrator will eventually reach, that is, the value that corresponds proportionally to the target signal, and adding the above integral system after the control system becomes steady, This improves the delay in response caused by the phase difference of the branch system, and it becomes possible to quickly reach the target position.

Although the above embodiment has been described as position control, it is clear that t″L may also be angle control.

[Brief explanation of drawings]

Fig. 1 is a block circuit configuration diagram of a conventional position control system, Fig. 2 (→ to (d) are shown in Fig. 1 and waveform diagrams of various parts to explain the operation of the next block circuit, Fig. sI 3 is a diagram of the present invention) A block circuit configuration diagram of the position control system according to FIG. Strain element, 2... Position detector, 3... Amplifier, 4... Drive circuit, 5... Integrator, 6, 7.9.
··switch. 11...Signal inverter (differential circuit), 1o...Switch\J1 diagram 2 Figure 3 Figure t

Claims (1)

[Claims] 1. Includes a relative displacement operation element and a displacement amount detector. In a position control method of a proportional-integral deaf closed-loop control system in which the amount of displacement is controlled, n open/close switches are provided on the input side and output side of the integrator that performs the above-mentioned integral action, and the target value of the closed-loop control system is A position control system comprising: a signal system for initially setting a signal corresponding to the integrator in the integrator; and a switch for opening and closing the signal system. 2. The position control system according to claim 1, wherein the specific sinusoidal displacement operation is comprised of an electrostrictive element.