JP5341554B2 - Positioning control unit, positioning control method, and positioning control program - Google Patents

Description

  The present invention relates to a positioning control unit that performs stage positioning control, a positioning control method, and a positioning control program.

  In recent years, it consists of a magnetic head inspection device that requires precise movement accuracy in sub-micron units, a positioning stage equipped with a piezoelectric actuator for minute positioning of inspection devices in the semiconductor field and the optical field, and a capacitive position detection sensor. Positioning devices are frequently used. Under such circumstances, a fine movement stage device using a piezoelectric actuator element has been proposed (see, for example, Patent Document 1).

  In the positioning control method of the fine movement stage device described in Patent Document 1, a deviation between the command value and the detection value of the current position detection means of the fine movement stage is calculated, and the deviation is determined in advance based on the voltage limit value of the piezoelectric actuator. If it is larger, open loop control is executed, and if the deviation is smaller than the coarse pitch, closed loop control is executed. Thereby, the stage is moved to a position corresponding to the command value in a short time without destroying the piezoelectric actuator.

  In the field of positioning control, a technique for controlling the speed including positioning has also been proposed (see, for example, Patent Document 2 and Patent Document 3). The piezoelectric body control device described in Patent Document 2 stores information in which an equivalent capacitance in a piezoelectric body is associated with a voltage applied to the piezoelectric body, calculates a charge amount to be injected into and released from the piezoelectric body based on the data, and calculates Based on the result, current is injected into and released from the piezoelectric body to control the speed of the piezoelectric body. Thus, the control accuracy is improved by using the equivalent capacitance of the piezoelectric body.

  The head positioning control device described in Patent Document 3 outputs a head position signal from a head reproduction signal, and controls VCM and MA. That is, a fine position signal and a rough position signal having different resolutions are output from the reproduction signal of the head, the MA control amount is calculated based on the fine position signal, and the VCM control amount is calculated based on the rough position signal. ing. Thus, the positioning control by the two actuators is performed so that the displacement of the MA does not become a disturbance of the coarse motion control system and the MA does not exceed the operating range.

JP 2003-288121 A JP-A-5-327052 JP 2006-147116 A

  However, although the above-described positioning apparatus can perform high-resolution control, it has not been sufficiently pursued to reduce the position error in the positioning process to the proper positioning speed and target position. The present invention has been made in view of such circumstances, and a positioning control unit that improves the positioning accuracy of the positioning process by controlling the movement amount of the positioning process based on a specific positioning speed, positioning It is an object to provide a control method and a positioning control program.

  (1) In order to achieve the above object, a positioning control unit of the present invention is a positioning control unit that performs stage positioning control in a closed loop with position detection, and is based on a specific positioning speed per control cycle. An operation amount calculation unit that calculates an operation amount; an output control unit that outputs the calculated operation amount; and a D / A conversion unit that converts the output operation amount from a digital signal to an analog signal. The positioning of the stage is controlled by driving the piezoelectric element by the analog signal.

  As described above, the positioning control unit of the present invention can calculate the operation amount per control cycle based on the specific moving speed, and can control the moving amount in the positioning process. As a result, vibration due to the positioning operation can be suppressed. In addition, it is possible to apply a drive signal having an optimum rise time according to the response frequency of the positioning device. As a result, positioning accuracy can be improved.

  (2) Further, the positioning control unit of the present invention further includes a position detection unit that detects a position for each control cycle, and the operation amount calculation unit detects the detected position so as to maintain the specific positioning speed. The operation amount per control cycle is calculated according to the above. Thus, the positioning control unit of the present invention calculates the operation amount per control cycle based on the detected position. In this way, movement at a constant speed is possible, and position errors in the positioning process can be minimized. As a result, accurate and quick positioning can be realized.

  (3) Further, in the positioning control unit of the present invention, the output control unit divides the calculated operation amount with time so that the integral value of one control period becomes equal and outputs the divided operation amount with a predetermined resolution. It is characterized by. As described above, the positioning control unit of the present invention outputs the operation amount per control cycle by dividing the operation amount with a predetermined resolution in terms of time. The signal divided and converted into an analog signal is output after being averaged over one control period by the integration effect of the piezoelectric element. Thereby, the precision of D / A conversion can be made higher than the resolution of the device, and the positioning precision can be further improved. For example, it is possible to move in units of 0.1 nm using a D / A conversion unit with a resolution of a position converted value of 1 nm. The resolution of D / A conversion refers to the minimum unit of convertible output unique to the D / A converter.

  (4) Further, a positioning control method for performing positioning control of the stage in a closed loop with position detection, the step of detecting the position every control cycle, and the operation amount per control cycle based on a specific positioning speed. A step of calculating, a step of outputting the calculated operation amount, a step of converting the output operation amount from a digital signal to an analog signal, and a step of driving a piezoelectric element by the analog signal. It is characterized by. Thereby, the vibration by positioning operation can be suppressed and the positioning accuracy can be improved.

  (5) The positioning control program of the present invention is a positioning control program for performing positioning control of the stage in a closed loop with position detection, and processing for calculating an operation amount per control cycle based on a specific positioning speed. And a process of outputting the calculated manipulated variable, causing the computer to execute, converting the output manipulated variable from a digital signal to an analog signal, and driving the piezoelectric element by the analog signal, thereby enabling the stage It is characterized by controlling the positioning of the. Thereby, the vibration by positioning operation can be suppressed and the positioning accuracy can be improved.

  According to the present invention, it is possible to suppress the vibration caused by the positioning operation and improve the positioning accuracy.

It is a block diagram which shows the structure of a positioning device. It is a flowchart which shows the characteristic operation | movement of a positioning device. It is a figure which shows the example of the output of (a)-(c) D / A conversion. It is a figure which shows the example of the output of (a)-(c) D / A conversion. It is a figure which shows the example of the output of (a), (b) D / A conversion.

(Configuration of positioning device)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Embodiment described below is an example and does not necessarily mean that this invention is limited to this. FIG. 1 is a block diagram illustrating a configuration of the positioning device 100. The positioning device 100 includes a PC 110, a controller 120, a stage driving unit 130, a stage 140, and a sensor 150.

  The PC 110 includes an input unit 111, and the input unit 111 receives an input specifying a position and a positioning speed from a user. The controller 120 (positioning control unit) performs processing such as calculation and output of an operation amount per control cycle and calculation of the current position. The controller 120 includes an operation amount calculation unit 121, a determination unit 122, an output control unit 123, a D / A conversion unit 124, an output counter 125, a driving amplification unit 126a, a detection amplification unit 126b, an A / D conversion unit 127, and a current A position calculation unit 129 is provided.

  The operation amount calculation unit 121 calculates the total operation amount from the difference between the input movement amount and the current position of the stage. Then, the operation amount of one control cycle is calculated from the designated positioning speed and the time of one control cycle. In that case, it is preferable to calculate the operation amount with an accuracy of a unit of 1 / n of the resolution of the D / A conversion unit 124. Thereby, the accuracy of the operation amount can be reflected in the positioning. In this way, the accuracy of the total movement amount is increased while appropriately maintaining the movement amount per control cycle. Note that the resolution of the D / A converter 124 is the minimum unit of output that can be converted by the D / A converter 124. By making the operation amount in one control cycle constant, the position error in the positioning process can be minimized, and positioning with high accuracy and high response can be realized. The specific positioning speed may be specified by the user, or may be a speed obtained by control. For example, a value obtained by dividing the total operation amount by the required number of control cycles may be set as the specific positioning speed.

  The determination unit 122 determines whether the calculated operation amount is smaller than the settling range. The settling range is a preset value and is a reference value for determining that the movement amount of the stage 140 has achieved the input movement amount. Thereby, the positioning device 100 repeats the periodic control until it is determined that the calculated operation amount is smaller than the settling range.

  The output control unit 123 divides the calculated operation amount with time so that the integral value of one control period is equal, and outputs the operation amount with the resolution of the D / A conversion unit 124. The integral value of one control cycle of the manipulated variable is a value obtained by integrating the output over time over one control cycle. It is preferable to output the manipulated variable by dividing the resolution of the D / A conversion unit 124 every 1 / n time of one control cycle. In that case, the D / A converter 124 is driven at a speed n times the control cycle. Thus, the resolution of positioning control can be improved by outputting the control amount of one time divided into n times. For example, when n = 10, the resolution of positioning control is improved by one digit.

  The D / A converter 124 is a so-called D / A converter, has a predetermined resolution as a device, and outputs a digital signal output as an operation amount divided in time every 1 / n of one control cycle. To analog signal.

  The output counter 125 repeats the time-divided output n times per control period according to the output calculated by the output control unit 123 and outputs the output as an analog signal. The driving amplifier 126a (piezo amplifier) amplifies the signal output from the D / A converter 124 at a predetermined magnification and applies the amplified signal to the stage driver 130. The detection amplifying unit 126b (sensor amplifier) amplifies a signal indicating the position of the stage 140 detected by the sensor 150. The A / D converter 127 converts an analog signal indicating the position detected by the sensor 150 into a digital signal. The current position calculation unit 129 calculates the current position based on a digital signal indicating the position.

  The stage driving unit 130 includes a piezoelectric element, and drives the piezoelectric element according to an analog signal to move the stage. The piezoelectric element is, for example, a laminated piezoelectric actuator. The stage 140 moves according to the displacement of the piezoelectric element. The stage 140 is configured to be movable by expansion and contraction of the piezoelectric element.

  The sensor 150 (position detection unit) detects the position of the stage 140 as a signal. As the sensor 150, a capacitance type position sensor that detects a change in the position of the stage 140 as a change in capacitance can be used. Note that the detection amplification unit 126b, the A / D conversion unit 127, and the current position calculation unit 129 constitute a position calculation unit 160. The position calculation unit 160 calculates the current position of the stage from the detection position of the stage detected by the sensor 150.

(Positioning device operation)
Next, the operation of the positioning device 100 configured as described above will be described. FIG. 2 is a flowchart showing a characteristic operation of the positioning device. The operation of the positioning device 100 is a closed-loop control accompanied by a positioning operation. First, the positioning device 100 receives an input of the movement amount from the user (step S1).

  Next, the total operation amount to be output to the stage 140 is calculated from the input movement amount and the calculated current position (step S2). Then, the operation amount per control cycle is calculated from the designated positioning speed (step S3). By controlling the operation amount for each control cycle, vibration can be prevented. Next, the calculated operation amount is compared with a predetermined settling range (step S4), and if the operation amount is equal to or less than the settling range, the process ends. On the other hand, when the operation amount is larger than the settling range, the output amount is calculated (step S5). At this time, the operation amount per control cycle is calculated by dividing the operation amount per 1 / n time of one control cycle with the resolution of the D / A converter 124 as a unit. Details will be described later.

  Next, the digital signal, which is the output amount divided and output in terms of time, is converted into an analog signal by the D / A converter 124 (step S6), and the drive amplifier 126a amplifies the signal and the stage driver 130 applied. Then, the piezoelectric element of the stage driving unit 130 is driven, the stage is moved based on the output amount (step S7), and it is determined whether or not the driving of the piezoelectric element has been completed n times (step S8). If the driving of the piezoelectric element has not been completed n times, the process returns to step S6. If the driving of the piezoelectric element has been completed n times, the position of the stage is detected (step S9).

  Next, the analog signal indicating the detection position is amplified and converted into a digital signal (step S10). The average value of the detected positions that have been digitally converted is calculated as the current position (step S11), and the process returns to step S2. Steps S2 to S11 are one control cycle. In the above example, the operation ends when the manipulated variable is less than or equal to the settling range in step S4. However, the control may be repeated to maintain the position of the stage as it is.

(Example of output to D / A converter)
Next, a method for calculating the output of the D / A conversion will be described below. FIGS. 3A to 3C are diagrams illustrating examples of D / A conversion output. In the figure, the horizontal axis represents time, and the vertical axis represents voltage. FIG. 3A shows an output when the D / A converter 124 outputs a resolution equivalent amount in one control cycle. Ten rectangular integration regions with numbers represent the total output. However, the actual driving is determined by the voltage. For example, when the stage driving unit 130 is driven and the stage 140 is moved by this, the moving distance is a driving amount corresponding to the resolution of the D / A conversion unit 124 such as 1 nm. It becomes. In the D / A converter 124, this amount becomes the minimum unit of conversion, that is, the resolution.

  However, in practice, the operation of the D / A converter 124 per control cycle can be divided and output every predetermined time. For example, as shown in FIGS. 3A and 3B, the output for each resolution can be controlled every time the control cycle is divided into ten. That is, as shown in FIG. 3B, the D / A converter 124 can output a voltage corresponding to the resolution for the first 1/10 time of one control cycle. In that case, the minimum unit voltage is applied to the piezoelectric element of the stage drive unit for the first 1/10 time of one control cycle.

  The piezoelectric element has an integration effect, and when such an output is present, the output is averaged over one control period. Therefore, when the output of FIG. 3B is applied to the piezoelectric element, the piezoelectric element is driven as much as the output shown in FIG. Thereby, the drive of a piezoelectric element can be controlled to the distance of 1/10 of the movement distance corresponding to resolution. In the above example, the output is controlled every time when one control cycle is divided into ten. However, the output may be divided into 100 or 1000, and if the output counter 125 has the ability to finely control, control according to time. Is optional. In this way, the D / A conversion method of performing signal processing by dividing the control period into n is applied to a capacitive load piezoelectric element having an integration effect.

  FIGS. 4A to 4C are diagrams illustrating an example of D / A conversion output in the case of outputting 5/10 of the resolution. In the example shown in FIG. 4A, the output is alternately performed or stopped every 1/10 time of one control cycle. In the example shown in FIG. 4B, the data is output in the first 5/10 control cycle and not output in the subsequent 5/10 control cycle. In any case, since the total output amount is represented by integration, as shown in FIG. 4C, the drive amount of the piezoelectric element by these outputs is 5/10 of the drive amount corresponding to the resolution, The same.

  FIGS. 5A and 5B are diagrams illustrating an example of D / A conversion output when 11/10 resolution is output. In the example shown in FIG. 5A, an output twice the resolution is D / A converted for the first 1/10 control period, and an output equal to the resolution is DA converted for the remaining time. Thereby, as shown in FIG. 5B, the driving amount of the piezoelectric element by the output in this case becomes 11/10 of the driving amount corresponding to the resolution. Similarly to this example, when it is desired to set the drive amount to 101/10 of the drive amount corresponding to the resolution, for example, the output of 11 times the resolution is D / A converted for the first 1/10 control period, and the rest What is necessary is just to D / A convert the output of 10 times the resolution with respect to time.

100 Positioning device 110 PC
111 Input unit 120 Controller (positioning control unit)
121 operation amount calculation unit 122 determination unit 123 output control unit 124 D / A conversion unit 125 output counter 126a drive amplification unit 126b detection amplification unit 127 A / D conversion unit 129 current position calculation unit 130 stage drive unit 140 stage 150 sensor 160 Position calculation unit

Claims (4)

A positioning control unit that performs stage positioning control in a closed loop with position detection,
An operation amount calculator that calculates an operation amount per control cycle based on a specific positioning speed;
An output control unit that divides the calculated operation amount in time so that integral values of one control period are equal, and controls output ON / OFF in units of resolution of D / A conversion for each division time ;
A D / A converter that converts the output manipulated variable from a digital signal to an analog signal;
A positioning control unit for controlling positioning of the stage by driving a piezoelectric element by the analog signal. A position detector for detecting the position for each control period;
The positioning control unit according to claim 1, wherein the operation amount calculation unit calculates an operation amount per control cycle in accordance with the detected position so as to maintain the specific positioning speed. A positioning control method for performing positioning control of a stage in a closed loop with position detection,
Detecting a position for each control period;
Calculating an operation amount per control cycle based on a specific positioning speed;
Dividing the calculated manipulated variable in time so that the integral value of one control period is equal, and controlling ON / OFF of the output in units of D / A conversion resolution for each divided time ;
Converting the output manipulated variable from a digital signal to an analog signal;
And a step of driving the piezoelectric element by the analog signal. A positioning control program for performing stage positioning control in a closed loop with position detection,
A process for calculating an operation amount per control cycle based on a specific positioning speed;
A process of dividing the calculated manipulated variable in time so that the integral value of one control period is equal, and controlling ON / OFF of the output in units of resolution of D / A conversion for each divided time. To run
A positioning control program that controls the positioning of the stage by converting the output operation amount from a digital signal to an analog signal and driving a piezoelectric element by the analog signal.

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