JPH0786150A - Positioning controller - Google Patents

Abstract

PURPOSE:To provide a positioning controller in which mechanical resonance is prevented and positioning time is shortened by a constitution wherein some positional deviation, i.e., offset, is left even immediately after switching of the target position from a temporary position to a true position. CONSTITUTION:The positioning controller comprises a position sensor 7 for detecting the current position of a stage 6, a counter 8, a differential unit 2 for calculating the deviation from a target position, a driver amplifier 4 for driving the stage 6 to the target position, and a servo motor 5. The positioning controller further comprises an overshoot detecting circuit 9, a register 1b for storing a true target position, a register 12 for storing the positional deviation, i.e., an offset amount, a register 1a for storing a temporary target position, and a switch 11 for switching the input to the differential unit 2 from the register 1a to the register 1b upon detection of peak overshoot. This constitution allows shortening of the positioning time without amplifying the mechanical resonance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a movable body positioning apparatus, and more particularly to a movable body positioning control apparatus that requires high-speed and highly accurate positioning of an XY stage or the like.

[0002]

2. Description of the Related Art Conventionally, a positioning control device of this type moves to the vicinity of a target position in accordance with a velocity curve as shown in FIG. 4, and then uses a control unit of the positioning control device as shown in FIG. Position control was performed. In the apparatus shown in the figure, the target position data from the target position register 1 and the current position data from the counter 8 are subtracted by the difference unit 2 to obtain a position deviation signal. After this position deviation signal is converted into an analog signal by the DA converter 3, it is input to the motor 5 via the driver amplifier 4 to drive the movable body 6 such as a stage. Then, the current position of the movable body 6 is detected by the position sensor 7 and the counter 8 and is fed back to the difference unit 2. In this way, the position of the movable body 6 is controlled to the target position set in the target position register 1 in the control device of FIG.

FIG. 5 shows a time transition of the position deviation signal in the control device of FIG. As is clear from the figure. In the control device of FIG. 3, since the first overshoot amount is usually large, the second and third overshoots or undershoots continue to occur, and the movable body 6
Had a disadvantage that the positioning vibration establishment time of became long.

In order to solve such a problem, Japanese Patent Publication Sho
There is a control method described in 63-49908. This control method will be described with reference to FIG.

The controller of FIG. 6 has registers 1a and 1 for storing a temporary target position and a true target position, respectively.
b, an overshoot detection circuit 9 for detecting the peak of the overshoot, an overshoot detection latch 1 for latching the output of the difference unit 2 as the peak amount of the overshoot at the time of the peak of the overshoot
0, and a changeover switch 11 for changing the target position from the temporary target position to the true target position when the overshoot reaches a peak. A temporary target shifted by the first overshoot amount from the true target position is set in the register 1a. The provisional target position is controlled until the movable body 6 approaches the target position, and when the movable body reaches the peak of overshoot, that is, when the speed of the movable body becomes zero. Use a control scheme that replaces the position with the true target position.

According to the method described above, since the position deviation is large until the position of the movable body approaches the target position, the position of the movable body is rapidly driven because the position deviation is large after the position of the movable body approaches the target position. It is said that the position will be rapidly reduced and the positioning will be completed rapidly without causing a large overshoot or undershoot.

[0007]

However, in the above-mentioned control method, in the case of a movable body where damping of mechanical resonance (mechanical resonance) is bad, acceleration of the velocity curve of FIG. 4 for moving to the vicinity of the target position. In order to rapidly approach the target position and replace the target position with the true target position before the mechanical resonance generated during deceleration converges, the remaining mechanical resonance is rather amplified as shown in FIG. However, there is a problem that the positioning time does not shorten as expected.

In view of the problems of the prior art, it is an object of the present invention to prevent amplification of mechanical resonance and shorten the positioning time in the positioning control device.

[0009]

In order to achieve this object, a positioning control device of the present invention comprises a movable body, means for detecting the current position of the movable body, and deviation of the present position from an input target position. And a means for driving the movable body toward the target position based on this deviation, and a predetermined offset amount is added to a very large amount of the first overshoot with respect to the target position during this driving. A means for outputting the difference between the quantity and the true target position as a temporary target position to the difference means, a means for detecting that the first overshoot has reached a maximum point, and the maximum point is detected by this means. And a means for switching the input target position to the difference means from the temporary target position to the true target position.

[0010]

In this configuration, an appropriate amount of offset is set in advance, and first, control is performed with a position shifted from the true target position by the first large amount of overshoot and the offset amount as a temporary target position. Then, when the movable body reaches the peak of overshoot, that is, when the speed of the movable body becomes 0, the temporary target position is replaced with the true target position, and the subsequent control is performed.

According to this, even after the target position is changed from the temporary target position to the true target position, a certain degree of position deviation, that is, the offset amount remains, so that the damping of mechanical resonance is not movable. Also in the body, the positioning control is performed without amplifying the remaining mechanical resonance, and the positioning time is shortened.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of a control system of a positioning control device according to an embodiment of the present invention. This apparatus includes a movable body 6 such as a stage, a position sensor 7 that outputs the amount of movement of the movable body 6 as an up / down signal by a rotary encoder, a laser interferometer, or the like, and the up / down signal to count the movable body 6. The counter 8 for obtaining the movement amount and outputting the current position, the difference unit 2 for calculating the deviation between the input target position and the current position from the counter 8, the DA converter 3 for converting the deviation into an analog signal, and the DA converter 3 A driver amplifier 4 that amplifies the output, a servo motor 5 that moves the movable body 6 according to the output of the driver amplifier 4, and an overshoot that detects that the overshoot has reached a peak based on an up / down signal from the position sensor 7. The detection circuit 9 outputs the output of the differential unit 2 at the time when the overshoot reaches a peak as the peak amount of the overshoot. Jiseul overshoot detection latch 10, register 1b for storing the true target position, the register 1 for storing the offset amount
2. A register 1a that stores the offset amount and the peak amount of the overshoot subtracted from the true target position as a temporary target position, and the overshoot detection circuit 9 detects that the overshoot reaches the peak. In addition, a changeover switch 11 for changing over the input to the differentiator 2 from the register 1a to the register 1b is provided.

In this structure, an appropriate offset amount is set in the register 12, and the first overshoot amount from the true target position and the offset amount set in the register 12 are set in the register 1a. Set the shifted value. That is, assuming that the temporary target position is Pi, the true target position is Pt, the first overshoot amount is d, and the offset amount is k, Pi is stored in the register 1a.
Temporary target position data P _{i of} = Pt-d-k is input. Then, the changeover switch 11 is set to a position where the output of the register 1a is connected to the input of the difference unit 2, and the positioning control operation is started in this state. Then, as shown in FIG. 2, the change in the current position in this case causes an overshoot of a peak amount d ′ when viewed from the tentative target position, and this overshoot is almost peaked at time t ₁ . The amount has been reached. Where d'is usually d
Is equal to Therefore, at time t ₁ , the current position approaches a position separated from the true target position Pt by the offset k.

At such time t ₁ , a switching signal is applied from the overshoot detection circuit 9 to the switching circuit 11,
The output of the register 1b that stores the true target position is the differencer 2
Connected to the input of. That is, the target position is switched from the provisional target position to the true target position, and there is a position deviation of k. In such a state, even if there is residual vibration due to mechanical resonance, positioning is quickly performed with respect to the true target position without amplifying this vibration.

The optimum value of the offset amount k differs depending on the nature of the movable body 6. Further, the optimum value of k may be a positive value or a negative value. As one method of obtaining the optimum offset amount k, the value of k is changed within a certain range to measure each positioning time, and the value of k when the positioning time is the shortest is set as the optimum value of k. There is a way.

The registers 12, 1a and 1b, the difference unit 2, the overshoot detection circuit 9, the overshoot amount latch 10, and the changeover switch 11 in the control device of FIG.
Etc. can all be replaced by one microprocessor. Further, the value of the offset amount set in the register 12 may be set to an optimum value depending on the moving distance and the moving direction of the movable body 6 and may be selected.

[0017]

As described above, according to the present invention, even after the target position is changed from the temporary target position to the true target position, a certain degree of position deviation, that is, an offset amount remains, so that mechanical resonance occurs. Even in a movable body with poor damping, the positioning time can be shortened and the positioning accuracy can be improved without amplifying the remaining mechanical resonance.

[Brief description of drawings]

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

FIG. 2 is a graph showing a temporal change of a current position in the device of FIG.

FIG. 3 is a block diagram showing a conventional positioning control device.

FIG. 4 is a diagram showing a conventional speed control pattern.

5 is a graph showing a temporal change of a current position in the device of FIG.

FIG. 6 is a block diagram showing another conventional positioning control device.

7 is a graph showing the change over time of the current position in the device of FIG.

[Explanation of symbols]

1: target position register, 1a: temporary target position register,
1b: True target position register, 2: Difference device, 3DA converter, 4: Driver amplifier, 5: Servo motor, 6:
Movable body, 7: Position sensor, 8: Counter, 9: Overshoot detection circuit, 10: Overshoot amount latch, 1
1: target position switching circuit, 12: offset register.

Claims (1)

[Claims] 1. A movable body, a means for detecting a current position of the movable body, a difference means for detecting a deviation of the current position with respect to an input target position, and the movable body based on the deviation. And a difference between the true target position and an amount obtained by adding a predetermined offset amount to a very large amount of the first overshoot with respect to the target position at the time of this driving, as the temporary target position. Means for detecting that the first overshoot has reached a maximum point, and when the maximum point is detected by this means, the input target position to the difference means is changed from the temporary target position to the true target position. A positioning control device comprising means for switching to a target position.