JPS60118818A - High-speed positioning device for stage - Google Patents

Abstract

PURPOSE:To enable smooth stopping of a stage in a target position by making the driving voltage of a DC motor zero just before the target position of the stage by a prescribed extent then driving the motor at a low speed until the stage arrives at the target position. CONSTITUTION:When the coordinate position of a stage 3 is instructed from an instructing device 2, a microcomputer 1 calculates the number N of pulses corresponding to the moving distance of the stage 3. A control signal for the number of pulses is then inputted to a pulse generator 5 so that the command pulses of the number N' smaller by a constant than the number N are outputted. A DC motor 10 begins to run and maintains the max. speed until the command pulses are inputted by the number N'. When the number of feedback pulses to a deviation counter 7 approaches to N', the speed of the motor 10 decreases and when said number attains N', the driving voltage is zero. The microcomputer 1 controls thereafter the command pulse generator so as to bring the stage to the target position. The stages stops smoothly in the target position.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a high-speed stage positioning device using a step drive method using a DC motor.

(Background of the Invention) A stage drive device f using a step drive method using a DC motor manually inputs a number of command pulses corresponding to the moving distance of a stage of a microscope or the like to the J terminal of a deviation counter.
Feedback pulses from a rotary encoder connected to the rotating shaft of the DC motor are input to the individual input terminals of the deviation counter.

The structure was such that the output of the deviation counter was converted into an analog signal by a digital-to-analog converter (hereinafter referred to as a D/A converter), and then a DC motor was driven via an amplifier or the like. Therefore, the output of the deviation counter is a value obtained by subtracting the number of command pulses and the number of feed pulses. 1When the two values are equal, the output becomes zero,
The outputs of the D and /A converters also become zero, and the DC motor stops.

That is, the DC motor stops when the number of feedback pulses equal to the number of command pulses has been generated.

Therefore, the stage will move a predetermined distance.

However, in the conventional high-speed positioning device of the drive device as described above, the number of command pulses corresponding to the moving distance of the stage is input and the motor is rotated by that amount, so deceleration is not performed smoothly. If the DC motor rotates beyond the target position, there will be more shift back pulses than command pulses, and as a result, the sign of the deviation counter output will be reversed, causing the DC motor to rotate in the opposite direction. In the worst case, the method has the disadvantage of causing transient response when the target position is not reached, and in the worst case, oscillation.

(Object of the Invention) An object of the present invention is to provide a high-speed stage positioning device that can eliminate the drawbacks of the conventional step drive method as described above and can smoothly stop the stage at a target position.

(Embodiment) FIG. 1 is a block diagram of an embodiment for positioning the stage of a microscope.

The microcomputer 1 receives a signal indicating the coordinate position of the stage 3 from the indicating device 2 and a rotation direction signal from the rotary encoder 4, and the pulse microcomputer 1 receives a pulse generator from these input signals according to the flowchart described later. The number of command pulses outputted by 5 and D/
The gain of the A converter 8 is controlled. The pulse generator 5 is
It is controlled by a pulse number control signal from the microcomputer 1 to output a corresponding number of pulses at a predetermined frequency.

The deviation counter 7 adds or subtracts the number of feedback pulses input from the rotary encoder 4 based on the number of pulses input from the pulse generator 5. The J)/A converter 8 outputs an analog signal corresponding to the count pulses of the deviation counter 7. This analog signal causes the DC motor IO to rotate via the amplifier 9. A lead screw is coupled to the shaft of the DC motor IO, and by screwing the nut of the stage 3 onto this lead screw, rotation of the DC motor 10 can be converted into linear movement of the stage 3. A rotary encoder 40 rotation axis is connected to the rotation axis of the DC motor 1o, and as a result,
The number of Salerhals (feedback pulses) output from the rotary encoder 4 corresponds to the amount of movement of the stage 3.

As is well known, a rotation direction signal (clockwise rotation, counterclockwise rotation) can be extracted from the rotary encoder 4. o - IJ-x 7 The feedback pulse of the coder 4 is input to the input terminal of the deviation counter 7 and also to the coordinate counter 6 as described above.

It is configured such that the coordinate values of stage 3 are measured.

Next, the operation shown in FIG. 1 will be explained with reference to the flowchart of the microcomputer 1 shown in FIG. 2 and FIG. 3, which is a speed curve of the DC motor 1o.

After initializing the stage 3, the coordinate counter 6 is reset, and the coordinate value ft(
When the microcomputer 1 specifies the coordinates set on the stage (for example, the coordinates where the observation optical axes intersect), the microcomputer 1 calculates the number of pulses N corresponding to the moving distance of the stage 3 (step 20), and the pulse generator 5 A pulse number control signal is manually applied to the pulse generator 5 so that a number N' (2N-a) of command pulses which is smaller than the number N of pulses by a constant a is outputted (step 21). When the number of command pulses of the pulse generator 5 reaches the number N' (step 22).

The rotational direction of the encoder is determined from the rotational direction signal from the rotary encoder 4 (step 23).

The DC motor 10 starts rotating with a predetermined number of command pulses, reaches the maximum speed Vs, and thereafter the command pulses and feedback pulses input to the deviation counter 7 are balanced.

The DC motor 10 maintains the maximum speed until a command pulse of several N' is input. This situation is shown in Figure 3.

In FIG. 3, the horizontal axis n represents the number of feedback pulses, and the vertical axis V represents the speed of the DC motor 10. As the number of feedback pulses approaches N', the number of pulses counted by the deviation counter 4 gradually decreases from the number of pulses required to maintain the maximum speed v8, so the speed of the DC motor 10 decreases. To go. When the number of feed bank pulses reaches N', the driving voltage of the DC motor 10 becomes zero, but due to inertia, the DC motor lO
The coordinate position corresponding to ′ is overstepped. As a result, the number of feedback pulses increases by N', so the number of pulses counted by the deviation counter 7 becomes negative.

A drive voltage is applied to the DC motor 10 so that it starts rotating in reverse. Then, the microcomputer 1 detects the moment when the DC motor 10 starts rotating in the reverse direction using the rotation direction signal of the rotary encoder 4.
The gain control signal is controlled so as to change the gain of the converter 8 from 1 to 0 (step 24). Next, the microcomputer 1 determines whether the number of pulses counted by the deviation counter 7 is positive or negative (step 25), and if it is positive, the D/A converter 6
The gain of is returned to 1 (step 26). If it is negative, the pulse generator 5 manually inputs command pulses to the deviation counter 7 until the number of pulses counted by the deviation counter 7 becomes positive (step 27). When the number of pulses counted by the deviation counter 7 becomes positive, the process proceeds to step 26, where the pulse generator 5 determines whether or not the number of command pulses is 111 months - 1A=N (step 28), where the number of command pulses is equal to the number N. If not, the pulse generator 5 is controlled so that the number N of command pulses is output (step 29). When the number of command pulses reaches N, the value of the coordinate counter 6 and the coordinate value of the indicating device 2 (step 29) are controlled. W
(Step 3oL match L)
If it is 7, the positioning is completed, and if it is not a match 1, some kind of trouble has occurred and a warning is given by an alarm (not shown) or the like (step 31).

In this way, the stage is accurately positioned at the coordinate position set on the pointing device 2 and stopped. If you want to move the stage from this stop position to another coordinate position, you can specify that coordinate position using the indicating device. The number N of pulses for moving the stage from this position to the latter coordinate position can be determined in step 20. The subsequent operations are exactly the same as in FIG.

In addition, the explanation for 9 or more is that in the case of a -dimensional stage, the t
However, it is also possible to perform the same operation on a two-dimensional stage, that is, a so-called XY stage.

In that case, the microcomputer 1 calculates the number of pulses Nx in the X direction and the number NY of pulses in the Y direction in step 20 of FIG. Do up to step 30,
After that, the same process may be performed on the Y-direction stage.

Furthermore, instead of controlling the gain of the D/A converter 8, the gain of the amplifier 9 may be controlled,
Mata. In place of rotary encoder 4, stage 3
It is clear that similar results can be obtained by using a linear encoder or the like that directly reads the amount of movement.

(Effects of the Invention) As described above, according to the present invention, there is provided a high-speed stage positioning apparatus using a step drive method.

Detects that the target position has been reached and sends a signal to the DC motor.
-Rather than applying power, the drive voltage of the DC motor is set to zero a predetermined amount before the target position, and then the motor is driven at low speed to the target position, so transient response can be minimized and the target position Therefore, it is possible to obtain a high-speed stage positioning device that can smoothly stop the stage.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the first embodiment of the present invention, FIG. 2 is a flowchart of the microcomputer 1 used in FIG. 1, and FIG. 3 is a diagram showing the speed curve of the DC motor 10 used in FIG. 1. , is. '(Explanation of symbols of main parts) 1...Microcomputer, 3...
f'/+4...Low encoder. 5...Pulse occurs! + 7... Deviation counter. 8...D/A converter. 10...DC motor. Applicant Nippon Kogaku Co., Ltd. Agent Takao Watanabe Figure 1-2

Claims (1)

[Claims] A stage, and an encoder means for outputting a feedback pulse every predetermined movement amount of the stage. a command pulse generator that outputs a command pulse corresponding to the amount of movement of the stage; and a DC motor for driving the stage in response to a difference between the feedback pulse and the command pulse becoming zero. A high-speed positioning device for a stage, comprising a driving means for reducing voltage to zero. The command pulse generator is controlled to output a predetermined number of command pulses corresponding to the desired movement amount of the stage, and when the sign of the feedback pulse changes, the driving voltage of the DC motor is made zero, and then the 1. A high-speed positioning device for a stage, comprising a microcomputer that controls the command pulse generator so as to add command pulses so as to achieve a desired movement amount of the stage.