JP2011221596A - Positioning device and positioning method for positioning stage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that when a setting range in case of positioning is set to zero, and positioning to a target value is performed, a motor always vibrates bit by bit even after a driven body is positioned to the target value by the motor, and the driven body is moved beyond the setting range due to disturbance in conventional positioning.SOLUTION: When a current value where a positioning stage detected by a position sensor is positioned is within a first setting range, the setting range of the positioning stage is changed to a second setting range, and when the current value where the positioning stage detected by the position sensor is positioned is beyond the first setting range, the positioning stage is moved again so as to be positioned within the first setting range.

Description

  The present invention uses a highly accurate linear scale sensor (linear encoder) for position detection in a positioning system used in semiconductor manufacturing / inspection equipment and optical equipment that requires precise movement accuracy, and high-resolution control as an actuator. The present invention relates to a precision positioning apparatus and a positioning control method using a possible ultrasonic motor.

  2. Description of the Related Art In recent years, in a magnetic head inspection apparatus that requires precise movement accuracy in sub-micron units and inspection apparatuses in the semiconductor field and the optical field, positioning composed of a positioning stage equipped with an ultrasonic motor capable of minute positioning and a linear scale sensor. Many devices are in use.

  For example, in Patent Document 1, a position command input from the outside is compared with a position feedback value, and the difference is set as a position deviation. When the absolute value of the position deviation exceeds a set threshold value, a fixed position gain is multiplied. A method of speed control by multiplying the position gain in two stages is shown in which, when the value is equal to or less than the threshold value, another position gain is selected from a correction pattern stored in advance, and the position gain is multiplied. In this way, the position settling time is shortened by correcting the position gain in accordance with the threshold value.

JP 2000-122724 A

  However, in the conventional positioning device as described above, since the drive source of the device is a servo motor, if the settling range at the time of positioning is always set to the target value with zero, the driven body is set to the target value by the motor. Even after positioning, the motor always vibrates in small increments and does not come to a standstill, so there was a problem in terms of durability of the motor. Even if the settling range for positioning is set to a certain width due to the above problems, the location within the settling range where the driven body is positioned is near the boundary between the settling range and outside the settling range. In such a case, there is a problem that the driven body is positioned outside the settling range due to small vibrations of the motor, or the driven body is moved outside the settling range due to disturbance such as external vibration. there is a possibility. Also in this case, the driving of the motor is stopped within the settling range, and the driving of the motor outside the settling range is repeated in a short time, which causes a decrease in the durability of the motor.

  The present invention has been made in view of such circumstances, and prevents the motor from generating irregular vibrations as in the conventional positioning device, so that stable positioning can be achieved even if there are disturbances such as external vibrations. It is an object of the present invention to provide a positioning device capable of

  In order to achieve the above object, the present invention detects a position sensor by moving a positioning stage by applying a signal obtained by converting an instruction value from a CPU by a D / A converter to an ultrasonic motor and driving it. The second settling range with the narrower one of the first settling range and the second settling range set as the settling range for the positioning is driven by feedback control that sends the current value of the moved positioning stage to the CPU. If the current value at which the positioning stage detected by the position sensor is within the first set range after positioning control of the positioning stage is within the first set range, the set range of the positioning stage is wider than the first set range. When the current value at which the positioning stage detected by the position sensor is outside the first settling range is changed to the second settling range, the first positioning stage is set again. It is characterized by moving so as to be located within the settling range.

  Thus, the present invention detects the current position (current value) of the positioning stage 6 with the linear scale 8 when an instruction value is given from an external host as shown in FIG. This is a positioning system that moves the positioning stage 6 by converting an operation amount into an analog signal by a D / A converter 3, amplifying it by a driver 5, inputting it to an ultrasonic motor 7, and driving it. When a signal that is detected by the linear scale 8 and sent to the CPU 2, an operation amount is calculated by the CPU 2, and analog conversion is performed by the D / A converter 3 is amplified by the driver 5 and a drive signal is input to the ultrasonic motor 7, linear When the current value at which the positioning stage 6 detected by the scale 8 is within the first settling range, the settling range of the positioning stage 6 is set to the first settling range. If the current value at which the positioning stage 6 detected by the position sensor is outside the first set range is changed to the second set range that is wider than the range, the positioning stage is again set within the first set range. It is characterized by controlling so that it may be located in.

  Preferably, when the current value at which the positioning stage is located fluctuates from the second settling range to outside the second settling range, the settling range of the positioning stage is changed to the first settling range, The positioning stage is moved again so as to be positioned within the first settling range.

  Here, the settling range at this time is stored in a memory (not shown). As the memory, a RAM built in the CPU 2 may be used, or it may be attached externally. The settling range is preferably set by measuring a settling range appropriate for controlling the positioning device in advance. Here, the settling ranges stored in the memory are the first settling range and the second settling range (the second settling range is wider than the first settling range), but a plurality of settling ranges are set. It may be stored in a memory and used properly for control.

  Preferably, the minimum value of the first settling range is set to the drive resolution amount of the positioning device.

  According to the present invention, the driven body (positioning stage) is necessarily positioned within the first settling range that is narrower than the second settling range. Positioning is completed within the center range within the settling range, and even if the driven body (positioning stage) is positioned outside the first settling range, positioning is performed within the second settling range. Will be completed. Therefore, the driven body (positioning stage) will not be out of the required settling range even if it is affected by disturbances caused by a small amount of external vibration, etc., which improves the durability of the motor and enables stable positioning control. Realize.

It is a block diagram which shows an example of the conventional general positioning device. It is a flowchart which shows operation | movement of the positioning device of this invention.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an example of a conventional general positioning apparatus, but the present invention is also implemented with a block diagram of the same configuration. FIG. 2 is a flowchart showing the operation of the positioning device of the present invention. The features of the present invention will be described with reference to FIGS.

  In the normal state, since the positioning stage 6 is closed-loop positioned at the origin position or the previous instruction value from the host PC 1, it is detected by the target value (instruction value) calculated from the position command command from the host PC 1 and the linear scale 8. Based on the current position (current value) of the positioning stage 6, the CPU 2 executes a positioning calculation for calculating an operation amount for each control cycle (for example, 1 ms).

  When a position command (instruction value) is input to the host PC 1 in order to move the positioning stage 6, the input position command (instruction value) is transmitted within the positioning device using RS232C communication as communication means capable of bidirectional communication. Although transmitted to the CPU 2, the CPU 2 in the positioning controller 4 obtains the current position (current value) of the positioning stage 6 with the linear scale 8 before the indicated value changes, and based on the indicated value from the host PC 1, PID calculation, etc. Positioning is performed as one control cycle until the amount of operation is calculated.

  In positioning the positioning stage 6 based on the position command (instruction value) from the host PC 1, the positioning stage 6 is positioned within a set range determined in advance by the user. Although it is necessary to set at least one range that must be maintained at least as a minimum, the stable positioning control can be performed by setting a plurality of setting ranges. Preferably, in addition to the widest setting range that must be absolutely maintained, a setting range narrower than that is set, and these setting ranges are preferably stored in a memory. Further, this memory may be a RAM built in the CPU 2 or may be externally attached separately.

The positioning method by the positioning device of the present invention will be described below based on FIG.
A position command (instruction value) is input to the host PC 1, and the input position command (instruction value) is transmitted to the CPU 2 in the positioning device using RS232C communication as communication means capable of bidirectional communication (Step 1). Here, a position command (instruction value) may be input to the host PC 1 in advance, and automatic control may be performed by a program that sets the host PC.

  Next, the positioning controller completes initialization, and during normal closed-loop positioning control, the current position (current value) of the positioning stage 6 used when calculating the operation amount (positioning calculation) for each control cycle. ) Is read by the linear scale 8 (Step 2).

  Next, the settling range of the positioning stage 6 is read from the RAM in which the information on the settling range of the positioning stage 6 is stored, changed to the first settling range and set (Step 3).

  Next, it calculates from the current position (current value) of the positioning stage 6 and the position command (instruction value) from the host PC 1 stored in the CPU 2 to drive the positioning stage 6 to the instruction value (Step 4).

  Next, the current position (current value) of the positioning stage 6 after positioning driving is read by the linear scale 8 and it is determined whether or not the current position (current value) of the positioning stage 6 is within the first settling range. (Step 5). When the current position (current value) of the positioning stage 6 is within the first settling range, the process proceeds to the next Step 6. On the other hand, if the current position (current value) of the positioning stage 6 is out of the first settling range, the process returns to Step 4 to drive the positioning stage 6 to the indicated value again.

  When the current position (current value) of the positioning stage 6 is within the first settling range at Step 5, the settling range of the positioning stage 6 is changed to the second settling range that is a settling range wider than the first settling range. To set (Step 6). Changing and setting the setting range of the positioning stage 6 to the second setting range, which is a setting range wider than the first setting range, widens the setting range, so that the ultrasonic motor moves within the setting range. The drive control is not accompanied.

  After the setting range of the positioning stage 6 is changed to the second setting range at Step 6 and set, the positioning is completed at Step 7 (Step 7).

  Even after the completion of the positioning in Step 7, the current position (current value) of the positioning stage 6 is always read by the linear scale 8, and the CPU 2 determines whether it is within the settling range. When the current position (current value) of the positioning stage 6 is located outside the second settling range that is wider than the first settling range, the process returns to Step 4 and the positioning stage 6 is moved again to the first settling range. Positioning drive within the settling range.

In this way, two other settling ranges (a settling range narrower than the required settling range) are set near the necessary settling range and the center point (positioning indication value) within that range, and the set value has hysteresis. (Set the setting value of the settling range to a different range), if the settling range is outside the required settling range, the settling range is changed (replaced) to another settling range, and positioning is performed. When the positioning stage comes to the position, the settling range is changed (replaced) to the necessary settling range, so that stable positioning is possible without generating unnecessary drive commands for the ultrasonic motor when holding the position after positioning is completed. Is possible.
Here, in order to stabilize the position holding, the first setting range may be set to a range narrower than the second setting range, but the minimum value of the first setting range is set to the driving resolution amount of the positioning stage system. It is preferable to do.

  By performing positioning control as described above, positioning of the positioning stage is completed at the center of the necessary settling range, and the necessary settling range is not deviated by a slight disturbance. For this reason, the fact that the ultrasonic motor continues to vibrate due to being positioned near the boundary of the settling range is reduced, and the durability of the motor is improved and stable positioning control is realized.

1 Host PC
2 CPU
3 D / A converter 4 Positioning controller 5 Driver 6 Positioning stage 7 Ultrasonic motor 8 Linear scale 9 Moving mechanism

Claims (4)

  The signal obtained by converting the instruction value from the CPU by the D / A converter is applied to the ultrasonic motor and driven to move the positioning stage, and the current value of the moved positioning stage detected by the position sensor is sent to the CPU. A positioning device that is driven by feedback control to send and controls positioning within a second settling range having a narrower range among the first settling range and the second settling range set as positioning settling ranges, and a position sensor When the current value at which the positioning stage is detected is within the first setting range, the setting range of the positioning stage is changed to a second setting range that is wider than the first setting range, and the position sensor If the current value at which the positioning stage is detected is outside the first settling range, the positioning stage is moved again so as to be positioned within the first settling range. Positioning device according to claim and.   If the current value at which the positioning stage is located fluctuates from the second settling range to outside the second settling range, the settling range of the positioning stage is changed to the first settling range, and the first positioning stage is set again. The positioning apparatus according to claim 1, wherein the positioning apparatus is moved so as to be located within a settling range of.   3. The positioning device according to claim 1, wherein the minimum value of the first settling range is set to a drive resolution amount of the positioning device.   The signal obtained by converting the instruction value from the CPU by the D / A converter is applied to the ultrasonic motor and driven to move the positioning stage, and the current value of the moved positioning stage detected by the position sensor is sent to the CPU. This is a positioning stage positioning method that is driven by feedback control to send and performs positioning control within the second settling range of the narrower one of the first settling range and the second settling range set as the positioning settling range. If the current value at which the positioning stage detected by the position sensor is within the first settling range, the settling range of the positioning stage is changed to a second settling range that is wider than the first settling range. If the current value at which the positioning stage detected by the position sensor is outside the first settling range, position the positioning stage again within the first settling range. Method for positioning a positioning stage, wherein the moving as.

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